A plate type catalytic reactor in which components of a starting material gas react comprises a plurality of pairs of heat transfer plates, each pair being formed of two sheets of corrugated plates joined to each other and each pair having a plurality of interior heat transfer medium flow passages, that are arranged so that projected surface parts and recessed surface parts of the corrugated plates of adjacent heat transfer plates are opposed to each other and so that the plurality of pairs of corrugated plates placed in contiguous non-contacting relationship define a plurality of catalyst bed regions in which catalyst material is placed, each having an inlet for the flow of starting gas material and an outlet for the egress of reaction product, wherein the direction of flow of the heat transfer medium through the passages is perpendicular to the direction of flow of starting material gas through the plurality of catalyst regions.