Disclosed are a laser device which uses alexandrite crystal and is capable of suppressing abnormal oscillation even if the size thereof is reduced and suppressing damage to an AR coating on a Q switch or alexandrite crystal, and a photoacoustic measurement device. A laser rod 11 includes alexandrite crystal. A flash lamp 12 irradiates the laser rod 11 with excitation light. A resonator includes a pair of mirrors 14 and 15 with the laser rod 11 sandwiched therebetween. A Q switch 16 is inserted into the optical path of the resonator and controls the Q value of the resonator. A polarizer 17 is inserted into the resonator and is a non-coated Brewster polarizer which selectively transmits light in a predetermined polarization direction among light emitted from the laser rod.