PURPOSE: To exchange a housing in a short time by providing a housing exchanging truck with which many housings which are clamped with a housing supporting table and housing clamp are lifted and moved between the position on the line and housing exchanging stations.

CONSTITUTION: The housing supporting table 21 on which many housings 4 for stretch reducer which is provided with rolls 9 for reducing a tube 8 can be supported in the line direction (20) is provided. A housing clamp 36 with which the upper parts of the many housings 4 which are supported on the housing supporting table 21 are restrained at once and the housing exchanging truck 35 with which the many housings 4 which are clamped with the housing supporting table 21 and housing clamp 36 are lifted and moved between the position on the line and the housing exchanging stations 32, 33 are provided.