A linear actuator that is configured to be extended/contracted by relatively displacing a first tube and a second tube in an axial direction, comprising: a rod that is provided inside the first tube; a plurality of permanent magnets that are held in the rod so as to be arranged in the axial direction; a stopper a coil that is provided inside the second tube so as to face the permanent magnets; and a stopper receiving portion that is provided on the second tube so as to contact with the stopper, said stopper having: a guide portion that is fixed to the rod; and a stroke defining portion that extends in the axial direction from the guide portion, the stroke defining portion having an extension-direction-side end surface, the extension-direction-side end surface contacting with the stopper receiving portion at a fully extended position, wherein the second tube includes a guide tube in which an inner circumference thereof is slidably fitted with an outer circumference of the guide portion, wherein the relative displacement between the first tube and the second tube in the extension direction is configured to be restricted by bringing an extension-direction-side end surface of the stroke defining portion into contact with the stopper receiving portion at the fully extended position, wherein a position of the permanent magnet and a position of the coil at the fully extended position are configured to be defined by bringing the extension-direction-side end surface of the stroke defining portion into contact with the stopper receiving portion at the fully extended position; characterized in that said stopper is provided at the tip-end of the rod. a rod that is provided inside the first tube; a plurality of permanent magnets that are held in the rod so as to be arranged in the axial direction; a stopper a coil that is provided inside the second tube so as to face the permanent magnets; and a stopper receiving portion that is provided on the second tube so as to contact with the stopper, said stopper having: a guide portion that is fixed to the rod; and a stroke defining portion that extends in the axial direction from the guide portion, the stroke defining portion having an extension-direction-side end surface, the extension-direction-side end surface contacting with the stopper receiving portion at a fully extended position, wherein the second tube includes a guide tube in which an inner circumference thereof is slidably fitted with an outer circumference of the guide portion, wherein the relative displacement between the first tube and the second tube in the extension direction is configured to be restricted by bringing an extension-direction-side end surface of the stroke defining portion into contact with the stopper receiving portion at the fully extended position, wherein a position of the permanent magnet and a position of the coil at the fully extended position are configured to be defined by bringing the extension-direction-side end surface of the stroke defining portion into contact with the stopper receiving portion at the fully extended position; characterized in that said stopper is provided at the tip-end of the rod. a guide portion that is fixed to the rod; and a stroke defining portion that extends in the axial direction from the guide portion, the stroke defining portion having an extension-direction-side end surface, the extension-direction-side end surface contacting with the stopper receiving portion at a fully extended position, wherein the second tube includes a guide tube in which an inner circumference thereof is slidably fitted with an outer circumference of the guide portion, wherein the relative displacement between the first tube and the second tube in the extension direction is configured to be restricted by bringing an extension-direction-side end surface of the stroke defining portion into contact with the stopper receiving portion at the fully extended position, wherein a position of the permanent magnet and a position of the coil at the fully extended position are configured to be defined by bringing the extension-direction-side end surface of the stroke defining portion into contact with the stopper receiving portion at the fully extended position;