A pilot operated electromagnetic valve comprising: - a body having a lead-in port through which a fluid is led in, a lead-out port through which the fluid is led out, and a main valve hole provided in a main passage joining the lead-in port to the lead-out port; - a driven member integrally formed with both a main valve element 44) and a piston, wherein the main valve element opens and closes a main valve by moving toward and away from the main valve hole and wherein the piston separates the main passage from a back pressure chamber; and - a pilot valve element that opens and closes a pilot valve by moving toward and away from a pilot valve hole, the pilot valve hole being provided in a sub-passage joining the lead-in port to the lead-out port by way of the back pressure chamber, - characterized in that the piston is configured by a piston body and a support such that the piston is divided, along a direction of axis line, into the piston body, which is formed integrally with the main valve element, and the support, which is provided separately from the main valve element, - wherein a piston ring, which slides along the body, is held between the piston body and the support, and - wherein the piston body is constantly in contact with one side face of the piston ring, and the support is constantly in contact with the other side face of the piston ring, the valve further comprising a biasing member that biases the support in a direction in which the support is brought close to the piston body, - wherein, the piston ring is held between the piston body and the support such that a predetermined clearance is formed between a surface of the piston body facing the support and a surface of the support facing the piston body in the direction of axis line, and the piston body and the support receive a biasing force exerted by the biasing member in the direction in which the surface of the piston body and the surface of the support are brought close to each other. - a body having a lead-in port through which a fluid is led in, a lead-out port through which the fluid is led out, and a main valve hole provided in a main passage joining the lead-in port to the lead-out port; - a driven member integrally formed with both a main valve element 44) and a piston, wherein the main valve element opens and closes a main valve by moving toward and away from the main valve hole and wherein the piston separates the main passage from a back pressure chamber; and - a pilot valve element that opens and closes a pilot valve by moving toward and away from a pilot valve hole, the pilot valve hole being provided in a sub-passage joining the lead-in port to the lead-out port by way of the back pressure chamber, - characterized in that the piston is configured by a piston body and a support such that the piston is divided, along a direction of axis line, into the piston body, which is formed integrally with the main valve element, and the support, which is provided separately from the main valve element, - wherein a piston ring, which slides along the body, is held between the piston body and the support, and - wherein the piston body is constantly in contact with one side face of the piston ring, and the support is constantly in contact with the other side face of the piston ring, the valve further comprising a biasing member that biases the support in a direction in which the support is brought close to the piston body, - wherein, the piston ring is held between the piston body and the support such that a predetermined clearance is formed between a surface of the piston body facing the support and a surface of the support facing the piston body in the direction of axis line, and