A multiwavelength optical sub-assembly module including a housing to be connected to an optical cable, a plurality of optical filter units coupled to the housing and configured to guide optical signals, a plurality of transceiver units coupled to the housing and configured to receive the optical signals through the optical filter units or transmit the optical signals to the optical filter units, and a substrate coupled to each of the transceiver units. Thus, distortion of an optical signal is suppressed, and the defect rate of a product is allowed to be decreased by evaluating reliability.