A feeder includes a conveyance path, a conveyance roller that conveys a sheet along the conveyance path, a transmitter that emits a space propagating energy, a receiver that receives a reflected energy obtained by reflection of the space propagating energy, and an actuator mounted pivotably on a pivot shaft and including first and second legs extending in different directions from the pivot shaft. The first leg is disposed to extend to the conveyance path and abut against the sheet being conveyed along the conveyance path. The second leg has a reflective surface crossing a path of the space propagating energy. The actuator is pivoted by abutment of the sheet against the first leg. The reflective surface is formed so that the reflected energy obtained by the reflection of the space propagating energy on the reflective surface enters the receiver regardless of an angle of pivotal movement of the actuator.