A temperature controller of an optical module package comprises an optical element and first thermistor fixedly held over a first Peltier element housed in an optical module package with a base interposed therebetween; a second thermistor housed in the optical module package; and a second Peltier element with the optical module package fixedly attached thereon with a mount interposed therebetween. While temperature control of the optical module package is achieved by monitoring the temperature of the optical module package with the second thermistor and controlling the second Peltier element, temperature control of the optical element is achieved by monitoring the temperature of the optical element with the first thermistor and controlling the first Peltier element. The temperature controller of the optical module package is impervious to the effect of open air temperature and capable of saving required space.