PURPOSE: To facilitate mounting of an engaging means held between front and rear cover plates of a console box or the like.

CONSTITUTION: In a mounting device having an engaging means to be fixed as being held by a front plate 4 and a rear plate 5, and the front and rear plates 4, 5, a locking structure to temporalily hold the engaging means at a predetermined position is provided on the rear side of the front cover plate 4 while the plates 4, 5 are ultrasonic oscillation fused, whereby the engaging means is fixedly held between the plates 4, 5.