Police were called to the scene at 7.52am today.
The flats, on Whitehall Quay, are part of the up-market Whitehall Riverside complex.
A West Yorkshire Police spokesman said the man had serious life threatening injuries and had been taken to hospital. It is unclear at this stage how the man came to fall from the fourth floor.
No-one else is understood to have been involved in the incident and police had cordoned off the scene while they conduct their investigation.