A thermal imaging device, comprising: a housing (3), which comprises a front housing (31); a lens mount (1), fixedly connected to the front housing (31), a sealing gasket (2) being provided between the front housing (31) and the lens mount (1); a lens (4), threaded with the lens mount (1); and a manual lens focusing structure, comprising a focusing wheel (8) and an axial positioning structure, wherein the focusing wheel (8) and the lens (4) are connected to each other in a synchronous rotation and relative axial movement mode, and the axial positioning structure implements axial positioning on the focusing wheel (8). In the process of focusing, the lens (4) axially moves with respect to the focusing wheel (8), and the focusing wheel (8) may not move axially due to the axial positioning structure.