A sheet feeder includes a sheet cassette insertable into a housing in a first direction, a remaining amount detecting member including a contact piece extending in a second direction opposite to the first direction and coming into contact with an uppermost sheet, and detecting a remaining amount of sheets according to a position of the contact piece, and a switching member switching the position of the contact piece between a contact position where the contact piece enters a storage space to come into contact with the uppermost sheet and a retracted position where the contact piece is retracted from the storage space. The position is switched to the contact position when the sheet cassette is inserted into the housing in the first direction and set to a feeding position while switched to the retracted position when the sheet cassette is separated from the feeding position and withdrawn from the housing.