To easily, quickly and inexpensively cope with various treatments by extending a tubular guide to replaceablely insert an optical fiber up to the front end part of a hand piece from the connecting side of the hand piece to a laser device.

The end part of an optical fiber projects by the length of a certain degree on the tip of a grip sleeve 13 of a hand piece. A rotary piston 15 is inserted into the grip sleeve 13, and a locking ring 16 is adhered. While a guide sleeve 18 is also inserted into the rotary piston 15, the press-fitting part 19 is slidably supported on the shaft direction in it so that the press-fitting part 19 is pushed in the stopper direction of the guide sleeve 18 by a spring 20. A pipe 21 also leads to the tip of the hand piece by passing through the grip sleeve 13 from the rotary piston 15.