The pure rotational spectrum of the CD2 radical in the (X) over tilde B-3(1) ground state was observed in the frequency region of 257 GHz-526 GHz by using a frequency modulated submillimeter-wave spectrometer. The CD2 radical was generated by the de glow discharge of deuterated ketene, CD2CO. Twenty one fine and hyperfine component lines of four rotational transitions were measured and were analyzed by a least-square method. Rotational and fine-structure constants were revised in higher accuracy than those of the previous laser magnetic resonance (LMR) study. The hyperfine coupling constants for the deuterium nuclei have been determined for the first time.