An expansion valve comprising: an inlet port through which a high pressure liquid refrigerant is introduced; a valve chamber communicating with the inlet port; a valve hole provided at an upper portion in the valve chamber; an outlet port through which the refrigerant expanded in the valve hole is discharged to the outside; a valve member that is brought close to and apart from a valve seat provided at an inlet of the valve hole and opens and closes the valve hole; and a coil spring provided in the valve chamber for biasing the valve member toward the valve hole, wherein a size of a space between adjacent coil wires of the coil spring is set so as to reduce bubbles entrained in the liquid refrigerant to a finder size, characterized in that the expansion valve further comprises a plug closing the lower end of the valve chamber and comprising a cylindrical spring support for supporting the coil spring; a support member supporting the valve member and capable of moving up and down; and the coil spring being provided below the support member in the valve chamber for biasing the support member toward the valve hole, wherein the support member has a recessed surface on an upper side, and a short shaft below the support member is inserted into the coil spring from the upper side such that the coil spring is mounted in a compressed state between the plug and the support member; the inlet port having a large diameter passage portion through which the liquid refrigerant is introduced and a small diameter passage portion communicating the large diameter passage portion and the valve chamber, wherein the large diameter passage portion and the small diameter passage portion are coaxially formed, the opening of the small diameter passage portion to the valve chamber being located in an inner wall of the valve chamber at a lower position than the support member and close to the coil spring, wherein the size of said space in an expanding and contracting direction of the coil spring is 0.54 mm or smaller in a state where the valve member abuts against the valve seat; and when the refrigerant flowing in through the large diameter passage portion and via the small diameter passage portion passes through the coil spring within the valve chamber, the bubbles in the liquid refrigerant having a diameter larger than said space is reduced to a finer size with a diameter smaller than said space. an inlet port through which a high pressure liquid refrigerant is introduced; a valve chamber communicating with the inlet port; a valve hole provided at an upper portion in the valve chamber; an outlet port through which the refrigerant expanded in the valve hole is discharged to the outside; a valve member that is brought close to and apart from a valve seat provided at an inlet of the valve hole and opens and closes the valve hole; and a coil spring provided in the valve chamber for biasing the valve member toward the valve hole, wherein a size of a space between adjacent coil wires of the coil spring is set so as to reduce bubbles entrained in the liquid refrigerant to a finder size, characterized in that the expansion valve further comprises a plug closing the lower end of the valve chamber and comprising a cylindrical spring support for supporting the coil spring; a support member supporting the valve member and capable of moving up and down; and the coil spring being provided below the support member in the valve chamber for biasing the support member toward the valve hole, wherein the support member has a recessed surface on an upper side, and a short shaft below the support member is inserted into the coil spring from the upper side such that the coil spring is mounted in a compressed state between the plug and the support member; the inlet port having a large diameter passage portion through which the liquid refrigerant is introduced and a small diameter passage portion communicating the large diameter passage portion and the valve chamber, wherein the large diameter passage portion and the small diameter passage portion are coaxially formed, the opening of the small diameter passage portion to the valve chamber being located in an inner wall of the valve chamber at a lower position than the support member and close to the coil spring, wherein the size of said space in an expanding and contracting direction of the coil spring is 0.54 mm or smaller in a state where the valve member abuts against the valve seat; and when the refrigerant flowing in through the large diameter passage portion and via the small diameter passage portion passes through the coil spring within the valve chamber, the bubbles in the liquid refrigerant having a diameter larger than said space is reduced to a finer size with a diameter smaller than said space.