A linear actuator includes a shell (10), an actuator mechanism (20), a telescopic tube (30) and at least one limit switch (40). An inner wall of the shell (10) has a guiding rail (11) formed thereon. The actuator mechanism (20) is disposed in the shell (10) and includes a motor (21) and a lead screw (22) driven by the motor (21). The telescopic tube (30) includes a nut (31) screwed with the lead screw (22) and an inner tube (32) integrally formed with the nut (31). The nut (31) has switching structures (311) and guiding slots (312) corresponding to the guiding rails (11). The limit switch (40) is fixed in the shell (10), and the limit switch (40) is capable of operating by a press of the switching structure (311). Therefore, the assembling of the linear actuator will be simplified for reducing sizes of components and occupied installation space.