A D-wave waveguide-planar circuit transition device comprises a rectangular waveguide, an anti-reflection waveguide, a back cavity, a transmission line shielding cavity and a dielectric base sheet, wherein the rectangular waveguide, the anti-reflection waveguide, the back cavity and the transmission line shielding cavity are of an interconnection waveguide structure, the anti-reflection waveguide is arranged at one end of the rectangular waveguide, the back cavity is arranged below the anti-reflection waveguide, the dielectric base sheet comprises a dielectric substrate and a metal layer, the metal layer is arranged on an upper surface of the dielectric substrate and comprises a transmission line, an impedance matching network and a probe, the probe is in an isosceles triangular shape, and a groove is formed in a top end of the probe. The D-wave waveguide-planar circuit transition device can work in a millimeter wave terahertz frequency band, is small in insertion loss, wide in applicable frequency band and small in circuit size, and is convenient to process and fabricate.