To enable an image forming apparatus which is mounted on a vehicle and has a vibration restraining mechanism, to easily switch between the state in which a holding part is fixed to the vehicle and the state in which the holding part is released from the fixed state.

A second support post 18 having a main body 20 is freely swingably held, via a vibration-proof mechanism 22, on a first support post 16 fixed to the cabin of the vehicle. The second support post 18 is provided with a first locking part 100 that is engaged with a bracket attached to the wall face of the vehicle and thereby restricts the swing displacement of the second support post 18 and main body 20. The connecting section of the first locking part 100 has in it a second locking part 102 capable of fixing the second support post 18 to the first support post 16. When subjects is photographed with the main body 20 after the vehicle is stopped, the main body 20 can be fixed to the vehicle with the first and second locking parts 100 and 102.