Patent ID: 8693009

Claim:
A rotation amount detecting device for a rotation body, comprising: a first rotation body provided with a first circumferential surface portion being in contact with a sheet being transported, the first rotation body rotating along with transportation of the sheet; a second rotation body provided with a second circumferential surface portion formed of a material different from a material forming the first circumferential surface portion and being in contact with the first circumferential surface portion, the second rotation body rotating along with rotation of the first rotation body; a first support member that rotatably supports the first rotation body at a first support position and swingably supports the first rotation body to swing around a first axis provided at a position different from the first support position of the first rotation body; a second support member that rotatably supports the second rotation body at a second support position and swingably supports the second rotation body to swing around a second axis provided at a position different from the second support position of the second rotation body, the second axis being any one of an axis provided to the first support member other than the first axis and an axis that is the same as the first axis; and a detector that detects an amount of rotation of the second rotation body.