Techniques capable of reducing the width-direction size of a phase shift circuit as much as possible are provided. A phase shift circuit has a signal line, a first dielectric plate, and a second dielectric plate. The signal line has first to third intersecting parts extending in a direction intersecting with a longitudinal direction of the phase shift circuit. On the other hand, the first dielectric plate and the second dielectric plate have first to third overlapping parts overlapping the intersecting parts of the signal line. When the first dielectric plate and the second dielectric plate are moved in the longitudinal direction of the phase shift circuit, the overlapped areas between the intersecting parts of the signal line and the overlapping parts of the first dielectric plate and the second dielectric plate are changed.