PURPOSE: To remarkably improve the burden in the measurement, by simply measuring the signal leakage of an adjacent channel and selecting the channel with a desired channel shift.

CONSTITUTION: The 1st channel number control circuit outputs a channel selecting signal with the input of a specific channel designation signal SC and a signal SS making continuous scanning. The 2nd channel number control circuit 15 outputs the 2nd channel selection signal based on the result of operation. The 1st and 2nd switching circuits 16 and 18 select switching bodies 16-1b, 16-2b∼18-1b and 18-2b corresponding to the channel based on the 1st and 2nd channel selection signals. When a test signal is generated from a signal source 17, the signal leakage from the 1st channel can be measured, since a level meter 19 is connected at the 2nd channel side via a body 20 to be tested and the switching body 18-2b.