PURPOSE: To reduce working man-hours by moving a positioning member to the inner circumferential surface of a counter by means of a drive member, causing a counter positioning member and the inner circumferential surface to abut on the positioning member and a sink positioning member respectively, and mounting a sink over these members.

CONSTITUTION: A counter 11, with its rear side faced outward, is placed on a mounting base of a device 1 for fixing sink and a drive member 5a is operated to move a positioning member 8 in a vertical direction. Guide pins 2 are disposed in a space of an opening 11a of the counter 11 and the pins are horizontally moved by means of a drive members 5b to cause a counter positioning member 4 to abut on the inner circumferential surface of the opening 11a. Thereafter, a sink 12 with a flange 12a to which a composite packing 7 is fixed is turned upside down and mounted on the rear side of the counter 11. The member 8 is moved horizontally and vertically by means of drive members 5a, 5b and the sink 12 is released from the counter 11 and then the sink 12 is bonded to the counter 11 with resin.