A semiconductor device, comprising: a main transistor (m0; M0) that is configured to supply power from a power source to a load; and a current limiting unit, including a control transistor (m2; M2), a sense transistor, a sense resistor, and a diode, wherein a source of the sense transistor is connected to a gate of the control transistor (m2; M2) and to one end of the sense resistor, a source of the control transistor (m2; M2) is connected to another end of the sense resistor and an anode of the diode, a cathode of the diode is connected to a source of the main transistor (m0; M0) and to one end of the load; a drain of the main transistor (m0; M0) and a drain of the sense transistor are connected to the power source, a gate of the main transistor M0 is connected to the gate of the sense transistor and the drain of the control transistor, wherein the current limiting unit has a current limit (Ith) value for determining that a current (i) greater than the operating current when the load operates in a steady state is flowing to the load, and is configured to detect that an overcurrent is flowing from the main transistor (m0;M0), and is configured to activate a current limiting function, when the current (i) is equal to or greater than the current limit value (Ith) and an CS voltage (V CS) between the gate of the control transistor (m2; M2) and the source of the control transistor (m2; M2) is equal to or greater than a threshold voltage (V th) of the control transistor (m2; M2), the control transistor (m2; M2) is configured to control the gate voltage of the main transistor (m0;M0) and has the current limiting function that limits the current (i) flowing through the main transistor (m0;M0) the current limiting unit is configured to set the current limit value (Ith) lower than the maximum momentary value (Im) of an inrush current occurring when the load is started up, and is configured to not activate the current limiting function when the CS voltage (V CS) is lower than the threshold voltage (V th) of the control transistor (m2; M2), even when the inrush current is equal to or greater than the current limit value (Ith). a main transistor (m0; M0) that is configured to supply power from a power source to a load; and a current limiting unit, including a control transistor (m2; M2), a sense transistor, a sense resistor, and a diode, wherein a source of the sense transistor is connected to a gate of the control transistor (m2; M2) and to one end of the sense resistor, a source of the control transistor (m2; M2) is connected to another end of the sense resistor and an anode of the diode, a cathode of the diode is connected to a source of the main transistor (m0; M0) and to one end of the load; a drain of the main transistor (m0; M0) and a drain of the sense transistor are connected to the power source, a gate of the main transistor M0 is connected to the gate of the sense transistor and the drain of the control transistor, the current limiting unit has a current limit (Ith) value for determining that a current (i) greater than the operating current when the load operates in a steady state is flowing to the load, and is configured to detect that an overcurrent is flowing from the main transistor (m0;M0), and is configured to activate a current limiting function, when the current (i) is equal to or greater than the current limit value (Ith) and an CS voltage (V CS) between the gate of the control transistor (m2; M2) and the source of the control transistor (m2; M2) is equal to or greater than a threshold voltage (V th) of the control transistor (m2; M2), the control transistor (m2; M2) is configured to control the gate voltage of the main transistor (m0;M0) and has the current limiting function that limits the current (i) flowing through the main transistor (m0;M0) the current limiting unit is configured to set the current limit value (Ith) lower than the maximum momentary value (Im) of an inrush current occurring when the load is started up, and is configured to not activate the current limiting function when the CS voltage (V CS) is lower than the threshold voltage (V th) of the control transistor (m2; M2), even when the inrush current is equal to or greater than the current limit value (Ith).