Image reading device capable of locking movement of carriage, image forming apparatus, locking member

An image reading device comprising:

• a housing including an exterior member and a document sheet placement surface on which a document sheet is placed, the exterior member forming an outer surface of the image reading device;
• a carriage configured to move in the housing along a predetermined specific direction, wherein either or both of a light source and a mirror that are used to read an image from the document sheet placed on the document sheet placement surface, are attached to the carriage;
• and
• a lock mechanism configured to lock the carriage to a predetermined lock position within a movement range of the carriage, wherein
• the lock mechanism includes:
• a supported portion supported by the housing and provided between the exterior member and the carriage disposed at the lock position;
• and
• a locking portion configured to move from either of a first position and a second position to the other so as to, at the first position, engage the supported portion with the carriage disposed at the lock position, and at the second position, release engagement between the supported portion and the carriage, the second position being closer to the exterior member than the first position, the locking portion moving from either of the first position and the second position to the other in response to a magnetic force of a magnet that is disposed at a specific position on the exterior member in a state of facing the supported portion across the exterior member.