To surely lock a cold reserving box with casters at nonusing time of the casters, and eliminate loss of a space occupied size due to projections of casters from the bottom face of the cold reserving box as in the past.

A Roberval mechanism is constituted on the bottom face of a cold reserving box main body A, of rotational moving links 3, 53, caster holding members 1, and bearings 2, 52 fitted to the bottom face of the main body. Casters C are fixed to the caster holding members 1. The rotational moving links 3 are connected to the handle arms 5 through intermediate link 4, and by operating the handle arms 5, the rotational moving links 3 are rotationally moved, so as to elevatably move the caster holding members 1. The handle arms 5 are fixed by fitting a lock bar 10 fitted to the handle arms 5 into the lock groove of an L-shape steel 8 provided on the main body.