A reading apparatus comprising: a reading unit (4, 4A, 4B); and a shaft that guides the reading unit (4, 4A, 4B) moving in a sub-scanning direction as a second direction, wherein the reading unit (4, 4A, 4B) extends in a main scanning direction as a first direction, perpendicular to the sub-scanning direction, and comprises: a reading portion for reading an image; a holding portion (6, 6A, 6B) that holds the reading portion, the holding portion (6, 6A, 6B) having a first surface (60, 80a, 90a); a sliding portion (5, 5A, 5B) that moves in contact with the shaft, the sliding portion (5, 5A, 5B) having a second surface (50a, 500) facing the first surface (60, 80a, 90a) in a third direction, perpendicular to the main scanning and sub-scanning directions; a first fixing portion for fixing the sliding portion (5, 5A, 5B) to the holding portion (6, 6A, 6B); a second fixing portion for fixing the sliding portion (5, 5A, 5B) to the holding portion (6, 6A, 6B), the second fixing portion provided at a distance in the main scanning direction from the first fixing portion; and a predetermined gap provided between the first surface (60, 80a, 90a) of the holding portion (6, 6A, 6B) and the second surface (50a, 500) of the sliding portion (5, 5A, 5B) in the third direction, wherein a first region is defined by the predetermined gap, and wherein the first region is located between the first fixing portion and the second fixing portion. a reading unit (4, 4A, 4B); and a shaft that guides the reading unit (4, 4A, 4B) moving in a sub-scanning direction as a second direction, wherein the reading unit (4, 4A, 4B) extends in a main scanning direction as a first direction, perpendicular to the sub-scanning direction, and comprises: a reading portion for reading an image; a holding portion (6, 6A, 6B) that holds the reading portion, the holding portion (6, 6A, 6B) having a first surface (60, 80a, 90a); a sliding portion (5, 5A, 5B) that moves in contact with the shaft, the sliding portion (5, 5A, 5B) having a second surface (50a, 500) facing the first surface (60, 80a, 90a) in a third direction, perpendicular to the main scanning and sub-scanning directions; a first fixing portion for fixing the sliding portion (5, 5A, 5B) to the holding portion (6, 6A, 6B); a second fixing portion for fixing the sliding portion (5, 5A, 5B) to the holding portion (6, 6A, 6B), the second fixing portion provided at a distance in the main scanning direction from the first fixing portion; and a predetermined gap provided between the first surface (60, 80a, 90a) of the holding portion (6, 6A, 6B) and the second surface (50a, 500) of the sliding portion (5, 5A, 5B) in the third direction, a reading portion for reading an image; a holding portion (6, 6A, 6B) that holds the reading portion, the holding portion (6, 6A, 6B) having a first surface (60, 80a, 90a); a sliding portion (5, 5A, 5B) that moves in contact with the shaft, the sliding portion (5, 5A, 5B) having a second surface (50a, 500) facing the first surface (60, 80a, 90a) in a third direction, perpendicular to the main scanning and sub-scanning directions; a first fixing portion for fixing the sliding portion (5, 5A, 5B) to the holding portion (6, 6A, 6B); a second fixing portion for fixing the sliding portion (5, 5A, 5B) to the holding portion (6, 6A, 6B), the second fixing portion provided at a distance in the main scanning direction from the first fixing portion; and a predetermined gap provided between the first surface (60, 80a, 90a) of the holding portion (6, 6A, 6B) and the second surface (50a, 500) of the sliding portion (5, 5A, 5B) in the third direction, wherein a first region is defined by the predetermined gap, and wherein the first region is located between the first fixing portion and the second fixing portion.