To provide a sheet feeder comprising a sheet cassette with a drawer section superior in operability, and an image forming apparatus.

The drawer section 60 is disposed in a sheet storage section body 50 of a sheet storage section 19 so as to be able to be pulled out. The drawer section 60 is pulled out when the sheet storage section body 50 stores a sheet larger than the sheet which the sheet storage section body 50 can store. A lock section 61 disposed on the drawer section 60 locks the drawer section 60 at a position where the drawer section is housed in the sheet storage section body 50 and at a position where the drawer section is pulled out from the sheet storage section body 50. The locking of the lock section 60 is released according to the pull-out operation and the housing operation of the drawer section 60.