PURPOSE: To realize the carry of a device by a comparatively simple constitution and place the device on a floor surface under a stable state during carrying by projecting/retreating a caster from/to the bottom of the device as occasion demands by utilizing a vacuum different pressure obtained by a vacuum pump, in a vacuum device having the vacuum pump.

CONSTITUTION: A caster 12 is connected to an air cylinder mechanism 26, which is installed slidably across the range from the retreat position in which the caster 12 is drawn back from the bottom surface of a box 2 to the advance position projected from the bottom surface of the box 2. This air cylinder mechanism 26 is connected to a pressure switching mechanism 30 for switching the inner pressure of the cylinder 22 in this air cylinder mechanism 26.