PURPOSE: To reduce a reclaimed container in volume without cutting by a method wherein a used synthetic resin container is heated as it is and crushed between crushing rolls.

CONSTITUTION: In a volume reduction device 1, a loading port 2 is opened on the upper part thereof, crushing rolls 8 made of a fixed roller 8a and a movable roller 8b are disposed below a duct 2a connected to the loading port 2, and a heating means 9 is provided between the duct 2a and the crushing rolls 8. The heating means 9 is, for example, made of a hot air blower. A container passed through the duct 2a is softened by hot air, thereafter being crushed and, simultaneously, cooled between the fixed roller 8a and the movable roller 8b to be extruded. In addition, it is desirable that an anti-sticking means is provided on the crushing rolls 8 and a cooling means is provided on at least one of them.