A man has been stabbed with a box cutter at Melbourne Central shopping centre in what police have described as a "shocking" daylight attack.

Police had to pull two men apart after the violent fight, which broke out outside a pharmacy in the CBD shopping complex, spilled onto the street about 1.30pm on Friday.

The 28-year-old victim was treated for upper body injuries and taken by ambulance to The Alfred hospital in a stable condition, an Ambulance Victoria spokeswoman said.

Two police officers pounced on the man's 40-year-old alleged attacker, pinning him to the ground.