Terahertz device includes first resin layer, columnar conductor, wiring layer, terahertz element, second resin layer, and external electrode. Resin layer includes first resin layer obverse face and first resin layer reverse face. Columnar conductor includes first conductor obverse face and first conductor reverse face, penetrating first resin layer in z-direction. Wiring layer spans between first resin layer obverse face and first conductor obverse face. The terahertz element includes element obverse face and element reverse face, and converts between terahertz wave and electric energy. Second resin layer includes second resin layer obverse face and second resin layer reverse face, and covers wiring layer and terahertz element. External electrode, disposed offset in a direction first resin layer reverse face faces with respect to first resin layer, is electrically connected to columnar conductor.