An optical module is produced by coating, with respect to a substrate having a substrate surface provided with terminal pads and landing pads a solder material on the terminal pads, mounting an optical element package having terminals and a flat top surface on the substrate using the landing pads so that the top surface becomes approximately parallel to the substrate surface and a gap is formed between a bottom surface of the optical element package and the substrate surface, preheating the terminal pads simultaneously as the mounting, and electrically connecting the terminal pads to corresponding terminals of the optical element package by melting the solder material and thereafter hardening the solder material.