PURPOSE: To reduce working man-hours by positioning and holding a counter and a sink by means of a positioning member and fixing the sink to the counter in that state.

CONSTITUTION: A positioning member 2, in which a sink positioning member 3 and a counter positioning member 4 are vertically provided, is provided in a space of an opening 11a of the counter 11 so that the member 3 protrudes from the rear surface of the counter 11. The member 2 is horizontally moved by means of a drive member 5 to cause the member 4 to abut on the inner periphery of the opening 11a. Then a sink 12 having a flange 12a to which a composite packing 6 is fixed is turned upside down to mount the sink 12 on the rear surface of the counter 11. The member 2 is moved horizontally and vertically by means of drive members 5a, 5b to bond the sink 12 to the counter 11 with resin.