PURPOSE: To improve the durability of the waveguide type optical module in a high-temp. atmosphere and to enhance the transmission characteristics thereof.

CONSTITUTION: This waveguide type optical module is constituted by fixing pedestals 2, 3, 4 into a housing 1, fixing a laser diode 5 as a light emitting element to the pedestal 2, a rod lens 6 to the pedestal 3 and an optical waveguide 7 made of quartz having, for example, 10mm width and 30mm length and a photodiode 8 as a light receiving element to the pedestal 4, respectively, introducing an optical fiber 11 via a sealing part 10 into the housing 1 and hermetically sealing the housing with a cap body 9. Two pieces of buffer materials 9a which prevent the peeling of the optical waveguide 7 from the pedestal 4 occurring in a difference in thermal expansion by pressing the optical waveguide 7 to the pedestal 4 when the cap body 9 is closed are mounted in parallel to the rear surface of this cap body 9.