A laser device includes a gain medium, a zero-degree reflective mirror, a first retro-reflective mirror, a second retro-reflective mirror, and an output coupling mirror. The gain medium is used to generate radiation light; the zero-degree reflective mirror has a common optical axis with the gain medium, and the zero-degree reflective mirror is used to totally reflect second-direction radiation light that is incident on the zero-degree reflective mirror in an optical-axis direction; the first-direction radiation light and the first emitted light are spaced from and parallel to each other in opposite directions; the first emitted light and the second emitted light are spaced from and parallel to each other in opposite directions; a resonant cavity is formed between the zero-degree reflective mirror and the output coupling mirror; the output coupling mirror is used to transmit and output first partial radiation light, and reflect second partial radiation light.