To determine whether a level of an image signal is lower in an upper heterodyne system receiving or in a lower heterodyne system receiving, even if an RF filter and an image removing mixer are used together.

An image signal level detector 1 comprises: a receiving control part 12 for controlling a tuning frequency of an RF filter 101 and an oscillating frequency of a local oscillator 102 in response to an instruction of a receiving system instruction part 11; a level detection part 15 for detecting a level of an output of a desired frequency signal removing mixer 13 for removing a signal of a desired frequency, via an IF filter 14; a level detection part 16 for detecting a level of an IF output of an image removing receiver 100; a difference detection part 17 for detecting a difference of outputs between the level detection parts 15 and 16; and a determination part 20 for determining whether, an output of the difference detection part 17 is lower in an upper heterodyne system receiving stored in a register 18 or in a lower heterodyne type receiving stored in a register 19.