A moisture content measurement device for measuring a moisture content in soil, comprising: a conductive wire structure which is insertable into soil, comprises insulatively-coated first and second conductive wires (11, 12) parallel to each other and extending adjacently and a ground wire parallel and extending adjacently to the first and second conductive wires and connected to a ground, and has a certain structure formed to have a size and a shape which is varied according to a size of an area to be measured; a leakage current measurement circuit configured to apply AC power to the first and second conductive wires and to measure a leakage current leaking through the ground wire; and a moisture content calculation unit (30") configured to calculate the moisture content in soil using the measured leakage current, wherein the leakage current measurement circuit comprise an AC power source, a first ammeter, a second ammeter, and a resistor, wherein the AC power source is connected between one end of the first ammeter and the ground and supplies an AC voltage, the first ammeter has the other end connected to the first conductive wire and measures a current I A1 supplied to the first conductive wire, the second ammeter has one end connected to the second conductive wire, and the resistor is connected between the other end of the second ammeter and the ground so that the second ammeter measures a current I A2 output through the second conductive wire, wherein a leakage current I leak, which flows through the ground wire, is measured by the difference between the current I A1 of the first ammeter and the current I A2 of the second ammeter. a conductive wire structure which is insertable into soil, comprises insulatively-coated first and second conductive wires (11, 12) parallel to each other and extending adjacently and a ground wire parallel and extending adjacently to the first and second conductive wires and connected to a ground, and has a certain structure formed to have a size and a shape which is varied according to a size of an area to be measured; a leakage current measurement circuit configured to apply AC power to the first and second conductive wires and to measure a leakage current leaking through the ground wire; and a moisture content calculation unit (30") configured to calculate the moisture content in soil using the measured leakage current, wherein the leakage current measurement circuit comprise an AC power source, a first ammeter, a second ammeter, and a resistor, wherein the AC power source is connected between one end of the first ammeter and the ground and supplies an AC voltage, the first ammeter has the other end connected to the first conductive wire and measures a current I A1 supplied to the first conductive wire, the second ammeter has one end connected to the second conductive wire, and the resistor is connected between the other end of the second ammeter and the ground so that the second ammeter measures a current I A2 output through the second conductive wire, wherein a leakage current I leak, which flows through the ground wire, is measured by the difference between the current I A1 of the first ammeter and the current I A2 of the second ammeter.