To provide a temperature compensation crystal oscillator in which the swell characteristics of frequency drift characteristics can be suppressed.

A crystal oscillator 5 and an inverter IC6 are connected in parallel, a voltage variable capacitive element 7 is formed across the parallel connection, the temperature is compensated by a temperature compensation circuit 1, frequency is compensated by an AFC2, frequencies in periods t1, t2, t3 are compensated, respectively, by frequency drift compensation circuits A3a, B3b, C3c, swelling of frequency drift characteristics is compensated by applying an offset voltage to the voltage variable capacitive element 7, and flat characteristics are achieved as the time elapses.