A sheet type discrimination device includes: a first light source unit that irradiates a sheet with light having a first wavelength and light having a second wavelength; a detection unit that detects light from the sheet and acquires a detection value based on the light; and a control unit that derives a determination result of a type of the sheet, wherein the first light source unit and the detection unit are located on a same side with respect to the sheet, the detection value includes: a first detection value; and a second detection value, and the control unit discriminates first-type recycled paper by first processing using the first detection value, and discriminates second-type recycled paper different from the first-type recycled paper by second processing using the second detection value.