A major expansion of Rottnest's main resort has been approved, with the West Australian Government hoping it will help attract new and old visitors to the island.

Hotel Rottnest will nearly double in size as part of the redevelopment, with an extra 80 rooms to be constructed.

The expansion will increase the resort's size to almost 18,000 square metres.

The $40 million redevelopment will see more "top-end" rooms become available, as well as additional "affordable" accommodation.

The redevelopment will add another 80 rooms to the resort. ( Supplied: Christou Design Group )

Room pricing has not been finalised, however.

Tourism Minister Paul Papalia said the development was long overdue.

"This expansion will deliver the resort experience that many guests have been calling for on Rottnest Island," he said.

"It will encourage new visitors and bring back people who may not have been to the island for years."

Australian actress Margot Robbie was one of 80,000 people to visit Rottnest in March. ( Instagram: Margot Robbie )

There will also be expanded function and conference facilities, a new restaurant and a rooftop bar.

"This space is going to transform the island and allow us to sell Rottnest as a world-class destination," Mr Papalia said.

"This doesn't take any accommodation away from the affordable end of the spectrum. It will add to the other end.

"A lot of the facilities will be available for everybody. It's not just something that's going to be an exclusive little enclave, it just provides an additional spectrum of offering."

The development will include a new pool and a rooftop bar. ( Supplied: Christou Design Group )

Not just 'one size fits all': developer

Developer Peter Prendiville said it would represent one of Rottnest's biggest-ever expansions.

"This allows us to cater to a broader range of needs, so it's not just a one size fits all," he said.

The approval of plans to expand the main resort comes amid the start of construction of a planned "glamping" site on the island.

The eco camping resort at Pinky's Beach is due to open in late 2018. ( Supplied: Baileys Group )

The eco tent resort will have around 80 tents, billed as a luxurious version of camping.

It is scheduled to open at the end of 2018, with tents ranging in cost from $100 to $350 a night.

Mr Prendiville said the hotel redevelopment would offer something different.

"The fact that corporates will be able to come and enjoy Rottnest Island, to enjoy what we as Western Australians have had for years, is significant," he said.

But he said the rooftop bar would not be "fine dining" and would be priced accordingly.

The Government said more than 80,000 people visited Rottnest in March, a 37 per cent increase on the same time last year.