A process for producing a circuit module including, carried out in this order, preparing a ceramic carrier substrate having ceramic substrate pads for mounting electronic parts, forming solder paste layers on the ceramic substrate pads, forming precoated solder layers by heating the ceramic carrier substrate having the solder paste layers on the ceramic substrate pads to melt the solder paste layers, and then cooling for solidifying the solder, preliminarily fixing stepped lid having protrusions adjacent to a cavity and dents adjacent to the cavity with the protrusions intervening therebetween to the precoated solder layers of the ceramic carrier substrate and joining the stepped lid to the ceramic carrier substrate with solder by placing the ceramic carrier substrate having the stepped lid preliminarily fixed to the precoated solder layers in a reflow furnace.