A processor module includes a first circuit substrate and a second circuit substrate each having a processor mounting area and a memory mounting area on one surface thereof. One processor is mounted in the processor mounting area, while comb-like arranged memory modules are mounted in the memory mounting area. The surface of the first circuit substrate and the surface of the second circuit substrate are combined face-to-face and positioned such that the processor mounting area and the memory mounting area of the first circuit substrate are placed face-to-face respectively with the processor mounting area and the memory mounting area of the second circuit substrate, and end parts of the plurality of comb-like arranged memory modules of the first circuit substrate and end parts of the plurality of comb-like arranged memory modules of the second circuit substrate are alternately arranged with clearances produced between adjacent memory modules.