The invention discloses a laser marking device and method. The laser marking device comprises a sample arm light path system, a detection light path system and a reference arm light path system. The sample arm light path system comprises a marking light source, a first collimating lens, a two-dimensional galvanometer set, a semi-reflective and semi-permeable mirror, a flat field focusing mirror, acarrying table and a first driving module. The reference arm light path system comprises a first optical fiber joint, a third collimating lens, a convergent lens and a reflective mirror. The detection light path system comprises a second optical fiber joint, a second collimating lens, a detection light source, an optical fiber coupler, a photoelectric detector and a computer processing terminal.The laser marking device is based on the interference principle and the optical coherence tomography; the depth position of a to-be-marked point on a sample is extracted; monitoring and focusing are conducted in real time; the carrying table is driven to move longitudinally; a focal plane is traced for marking; the device is simple in light path, low in energy consumption and high in automation degree and precision; and the production efficiency and production quality of laser marking are effectively improved.