The present invention provides an optical transmitting module, in which a laser diode and a termination resistor are provided without sizing up the package thereof and degrading the thermal characteristic due to heat generation by the termination resistor. The transmitting module of the present invention includes the semiconductor laser diode, and the resistor. The laser diode is mounted on the side surface of the block extruding from the base. The resistor is mounted on the flat side portion of the end of the lead. The lead is secured in the through hole provided in the base with seal glass being filled in the gap between the through hole and the lead. In the transmitting module thus configured, the laser diode is thermally isolated from the heat generated by the resistor due to the seal glass.