A biological information acquisition device includes a light source configured to emit a laser beam; a light branching element configured to branch the laser beam into a first luminous flux and a second luminous flux; a first light receiving element configured to receive the first luminous flux; a second light receiving element configured to receive scattered light generated by scattering of the second luminous flux incident on an inspection site of a living body; a differential circuit to which the first light receiving element and the second light receiving element are coupled; a signal processing unit configured to obtain biological fluid information by processing a light detection signal output via the differential circuit; and a first light shielding part configured to reduce the scattered light incident on the first light receiving element.