This study reports the observation of the carrier-tunneling-induced photovoltaic (PV) effect in an InAs/GaAs quantum-dot solar cell (QDSC). The illuminated current-voltage (J-V) characteristics and the applied-bias-dependent electroreflectance (ER) were measured at 12 K by using an excitation laser with a wavelength of 975 nm (1.27 eV), which excites only the quantum-dot (QD) states below the GaAs band gap. The J-V results showed a peculiar current curve in the reverse bias region caused by carrier tunneling. The ER results showed that the junction electric field (F) decreased with increasing intensity of the excitation laser (Iex) at different applied-bias-voltages (Va) due to the tunneling-induced PV effect. The PV effect was enhanced by improved tunneling with increasing reverse bias voltage. We also evaluated the tunneling carrier density (σpv) as a function of Va in the QDSC.