Proposed is a millimeter-wave band communication device which does not generate spatial resonance in a cover shielding unnecessary radio waves from the outside.Disclosed is a millimeter-wave band communication device including: a substrate; a radio frequency circuit element for a millimeter-wave band provided on the substrate; and a cover made of a bulk material that covers at least a part of the radio frequency circuit element and a surface of the substrate, the cover being formed by blending a dielectric loss material in a base.