A window cleaner was seriously injured when he fell three storeys from the Apple Store in Sydney's CBD and struck a bus shelter before landing on the ground.

The man, believed to be aged in his 40s, was taken to St Vincent's Hospital with injuries to his pelvis, spine and head after the accident on George Street about 8.30pm on Wednesday.

A hospital spokeswoman said the injured man was in a stable condition in hospital on Thursday morning.