To conduct shading correction with high accuracy by using a white reference member moving means to move a white reference member from a standby position to a read position only when white reference data for shading correction are acquired.

A white reference sheet 30 is configured to be movable at a standby position and a read position with a sheet drive mechanism 31, and the sheet 30 is placed in a pressing plate 5A above an original guide 33 in the standby state, projected in a direction of an original carrying path 35 in the reading state and intruded between a contact glass 12 of a close contact image sensor 9 and a rear side roller 10. That is, the white reference sheet 30 is fixed by an are 39 of the sheet drive mechanism 31 and the arm 39 is fitted turnably to the press plate 5A via a shaft 40. Thus, deposition of dust onto the white reference sheet 30 is prevented and the white reference sheet 30 without dust or dirt deposition is read and proper white reference data are acquired and shading correction is conducted with high accuracy.