Abstract: An object is to realize optical signal transmitter-receiver module with high transmitting power and high receiving sensitivity at a low cost. The optical signal transmitter-receiver module 60 includes a planar lightwave circuit (PLC) 61 and a transmitter-receiver circuit. The PLC 61 is made up with a Si substrate 62, a laser diode (LD) 6 generating the optical signal Pt, and a photodiode (PD)7 receiving the optical signal Pr. Both LD 6 and PD 7 are arranged on the Si substrate 62. The LD6 is arranged such that its front face is located in the vicinity of an optical fiber 64. The LD 6 has an optical waveguide layer that is composed of an active layer generating the optical signal Pt and a clad layer functioning as a transparent layer to the optical signal Pr. The PD 7 is arranged such that its front face is located in the vicinity of the backside face of the LD 6 and receives the optical signal Pr having passed through the optical waveguide layer of the LD 6.