the present invention discloses a method of melt - adhering a hard resin product to a substrate , wherein : a primer which includes a silane coupling agent is applied to a substrate which includes silicon , a hard resin product contacts a portion to which the primer has been applied , and the resin product is vibrated while pressure is applied thereto , and a melt - adhering apparatus which uses this method . a melt - adhering apparatus , comprising : a melt - adhering gun which includes a horn which can hold a resin product ; a nipping stand which is movably disposed beneath the horn so that a substrate is nipped between the nipping stand and the horn ; moving means which relatively moves the melt - adhering gun and the nipping stand ; and a converter which subjects the horn to ultrasonic vibration in response to an input signal . in the present invention , the resin product can be securely melt - adhered to the substrate inexpensively .