Quantum dots (QDs) are one of the promising candidates of interconnection between electromagnetic field and electrons in solid-state devices. Dark states appear as a result of coherence between the electromagnetic fields and the discrete energy levels of the system. Here, we theoretically solve the steady-state solutions of the density matrix equations for a thee-level double QD system and investigate the condition of the appearance of a dark state. We also numerically show the appearance of the dark state by time-dependent current characteristics. (C) 2012 The Japan Society of Applied Physics