The hammer tacker includes a shell, a handle, and a striking mechanism. The shell is made of a mixture of fiberglass and nylon by injection molding. The shell encloses a receiving room and has a bottom opening extending along the longitudinal direction of the shell and communicating with the receiving room. The handle is disposed on the rear end of the shell. The striking mechanism is made of metal and includes a magazine and a striker. The magazine is received in the receiving room. An end of the magazine is pivotally connected to the rear end of the shell, and the other end tends to move outward due to an elastic element. At end of the striker is disposed on the inner wall of the shell. When the magazine is hit upward, the striker strikes the nails out.