A short-pulse laser device (1) with passive mode locking, a laser resonator fed with a pumping beam (3), a laser crystal (4), especially a titanium sapphire (Ti:S) laser crystal, and laser mirrors (M1-M7) wherein the laser crystal (4) is exposed to a heat load after focusing of the beam, mounted on a heat dissipator (10) for heat elimination and presenting a bore hole (13) letting the laser beam (3; 8) pass through. In order to improve heat elimination, an especially waferlike crystal mount made of good heat conducting material, preferably copper, is fixed to the heat dissipator (10). The laser crystal (4) is held in an opening (14) of the mount (11) placed in a lateral position against the opposite walls (15, 16) of the mount (11) and the opening (14) of the mount (11) is aligned with the bore hole (13) in the heat dissipator (10).