To provide an auxiliary device capable of easily moving, positioning and horizontally adjusting an air conditioner.

A carriage 20 has plural (four) casters (adjustable) 6 on a bottom part 21a of a loading place 21, and at least one of the casters is a caster 6A with locking function. The carriage 20 is formed by attaching an anti-slip member 22 on an upper face of the loading place 21, and fixing L-shaped drop preventing members 23 on four corner parts. A mounting height of the casters 6 (6A) are finely adjusted by allowing screw parts 10 screwed on the bottom part 21a of the loading place 21 to come in and out, whereby the air conditioner is leveled while confirming a horizontal state of a level 5 placed on an upper face of the air conditioner 1. Whereby the air conditioner can be moved with small force, and positioned at a fixed position even though the external force is added, and the safety can be ensured by adjusting the level of the air conditioner.