IMAGE READING UNIT, IMAGE READING DEVICE, AND IMAGE FORMING DEVICE

To reduce stray light with a simple configuration.SOLUTION: An image reading unit (50) includes: a housing (51 or 52a) that holds a reading unit (59a) and has an entrance (701) through which light reflected by an object passes; and a reflection member (54) that has a reflection surface (54a) for reflecting the light which has passed through the entrance and forms an optical path which guides the reflected light from the object to the reading unit. The housing is provided with an opening that passes through from the inside to outside of the housing. The reflection member is held on the outside of the housing with respect to the opening so that at least part of the reflection surface is exposed to the outside of the housing via the opening.SELECTED DRAWING: Figure 3 【課題】簡素な構成により、迷光を低減する。【解決手段】画像読取ユニット（５０）は、読取部（５９ａ）を保持し、対象物によって反射された光が通過する入口（７０１）を備えた筐体（５１，５２ａ）と、入口を通過した光を反射する反射面（５４ａ）を有し、対象物からの反射光を読取部に導く光路を形成する反射部材（５４）と、を備える。筐体には、筐体の内側から外側に貫通する開口部が設けられている。反射部材は、反射面の少なくとも一部が開口部を介して筐体の内側に露出するように、開口部に対して筐体の外側に保持されている。【選択図】図３