To provide a compact and thin high-frequency module, and to provide a method of manufacturing the high-frequency module.

The high-frequency module 1 includes a package 2 with a semiconductor 6 mounted on one surfaces thereof and having a first conductor 52 including a planar line 521 to which a signal input/output terminal 61 of the semiconductor 6 is connected on the same plane as the semiconductor mounted surface and a planar line-waveguide converter 522, and a second conductor 53 covering the planar line-waveguide converter 522 on the other surface, wherein the second conductor 53 has a package2 connected with the first conductor 52 through first a through-hole 54 and an substantially rectangular second through-hole 31, and the second through-hole 31 has a circuit board 3 oppositely provided to the planar line-waveguide converter 522 of the package 2 and a conductive connection 41 arranged for connecting a ground area of the first conductor 52 in the package 2 with a ground of the circuit board 3 and surrounding the second through-hole 31.