A sheet feeder, including; a sheet holding portion; a sheet supply portion; an inclined member having an inclined surface and configured to guide each sheet in a sheet feed direction; and separation protrusions which are provided on the inclined member and each of which protrudes from the inclined surface such that a distal end thereof is located more downstream in the sheet feed direction than a proximal end thereof, wherein each separation protrusion has a contact surface and said each sheet comes into contact with one or more contact surfaces of the separation protrusions, and wherein each separation protrusion protrudes from the inclined surface such that the distal end of one of the separation protrusions is located more downstream in the sheet feed direction than the proximal end of another of the separation protrusions that is located immediately downstream of the one of the separation protrusions in the sheet feed direction.