PURPOSE: To remarkably reduce the power required for a heating element by expanding and reducing the full width of side member and supporting plate by moving the side member to a central member in the manner of nesting.

CONSTITUTION: A supporting plate B is provided with two side members 30 and 32, and these side members 30 and 32 are held in slots 34 and 36 formed at respective side edge parts 38 and 40 of a central member 22 in the telescopic (nesting style) relation. The dimension of a supporting plate B' is selected so that side edge parts 66 and 67 thereof can be matched with edge parts 53 and 54 formed between a first surface 42 of a press plate L and side press surfaces 50 and 52 when both arm members 60 and 61 are located at expanded positions. When both the arm members 60 and 61 are expanded like this, the portion of a garment placed around the side edge parts 66 and 67 can be pressed as well. By pressing the press plate L onto the supporting plate B, a pressing surface continued in respect to the supporting plate B is formed and even when the supporting plate B is expanded by the side members 30 and 32, all the surface on one side of a shirt S can be continuously pressed.