Provided are an optical sensor having a wider dynamic range with reduced temperature dependence, and a display apparatus in which these optical sensors are used. An optical sensor includes an accumulation node (INT); a reset signal line (RST); a readout signal line (RWS); a photodiode (D1) (photodetecting element); a photodiode (D2) (reference element) that has a light-shielding layer; a thin-film transistor (M1) (first switching element) that outputs a potential of the accumulation node (INT) in response to the readout signal during a sensing period; and a thin-film transistor (M2) (second switching element) that is provided between the accumulation node (INT) and the photodiode (D2), and that electrically separates the accumulation node (INT) from the photodiode (D2) when the potential of the accumulation node (INT) upon supply of the readout signal is higher than a potential on a side of the photodiode (D2) opposite to the accumulation node (INT).