The on-vehicle device includes: an oscillation unit configured to output a clock signal; at least one calculation unit configured to operate on the basis of the clock signal; a temperature sensor; a load estimation unit configured to estimate a load on the calculation unit, and on the basis of the estimated load, estimate whether or not there is a possibility of temperature increase in the calculation unit; and a clock setting unit configured to set a frequency of the clock signal to be outputted from the oscillation unit, wherein the clock setting unit decreases the frequency of the clock signal, if the load estimation unit estimates that there is a possibility of temperature increase in the calculation unit, and the temperature measured by the temperature sensor is equal to or greater than a predetermined temperature.