The photonic-crystal surface-emitting laser is a new-generation semiconductor laser capable of emitting a high-power, high-quality (i.e., high-brightness) beam, as well as on-chip two-dimensional beam steering, lasing in various wavelength regimes, and on-chip ultra-short self-pulsation, owing to their freedom of light-matter control. Here we introduce light detection as a new functionality, wherein the photonic-crystal laser is operated under reverse-bias conditions. We find that the photonic-crystal laser operated under reverse-bias conditions has a very high shunt resistance and a low dark current, which are essential qualities to achieve high detectivity. In addition, high responsivity is achieved by utilizing proper band-edge-modes and Q-matching conditions for resonant light absorption. Furthermore, by employing photonic-crystal lasers as the detector as well as the laser source, a direct time-of-flight distance measurement is successfully demonstrated.