The THz device module includes: a substrate; a THz device disposed on a front side surface of the substrate, and configured to oscillate or detect THz waves; a cap covering the THz device being separated from the THz device, and comprising an opening formed at a position opposite to the THz device in a vertical direction of the front side surface of the substrate; and a sealing member covering the opening of the cap so as to seal the THz device in conjunction with the substrate and the cap. A distance from the THz device to the sealing member is within a near-field pattern to which an electric field of the THz waves can be reached without interruption from a surface of the THz device to the sealing member. The THz device module efficiently emits or detects THz waves from the opening, thereby suppressing upsizing of the cap.