Room‐temperature operation of ZnSe‐active‐layer double heterostructure laser diode has succeeded. The lasing wavelength was 471 nm. The emission energy shift with the increasing current is explained by the band filling and the band shrinkage. The threshold carrier density is calculated to be 4×1018cm−3. The mechanism of the stimulated emission of II–VI double heterostructure laser diode is concluded to be the recombination of the electron‐hole plasma. ©1995 American Institute of Physics.