PURPOSE: To omit the use of an equipment of a large scale by changing the temperature within a range where the characteristic of a temperature compensated oscillation circuit is assured and producing automatically the correction value at each temperature point to automatically produce a temperature correction table.

CONSTITUTION: A phase comparison means 40 and a signal generating means 50 are added to a temperature compensated oscillator TCO for the formation of a phase locked loop. Then the temperature is changed within a range where the characteristic of the TCO is assured. The means 40 confirms a phase locked state every time a change detecting means 60 detects the change the minimum one unit. The value pointed by the means 50 then is equal to the wanted correction value. This correction value is written into an address designated by the temperature measurement value in a temperature correction table memory 30. Thus a temperature correction table is automatically produced. Consequently, the use of a measuring instrument and the computer system of large scales can be also omitted.