The invention discloses a passive mode-locked laser device which comprises a pumping light source, a pumping coupling device and a resonant cavity which are arranged along a light path in sequence, wherein the resonant cavity comprises a light input cavity mirror, a gain medium as well as a first saturable absorber mirror and a second saturable absorber mirror which form oscillating light in the resonant cavity; the first saturable absorber mirror is a reflective saturable absorber mirror which takes graphdiyne as a saturable absorption body; the second saturable absorber mirror which takes the graphdiyne as the saturable absorption body serves as a light output cavity mirror. According to the laser device, stable oscillation of light beams in the cavity is realized and maintained through the first saturable absorber mirror and the second saturable absorber mirror to obtain a continuous mode-locked pulse; the graphdiyne is taken as the saturable absorption body of the saturable absorber mirror, light can be selectively absorbed within a relatively wide wavelength range due to the light absorption bandwidth of the graphdiyne, and the wavelength range of an output pulse of the passive mode-locked laser device can be extended.