An RF coil apparatus suitable for a high magnetic field MRI apparatus includes a plurality of subcoils arranged substantially in a cylindrical form. Each subcoil includes a first conductor part and a second conductor part. The second conductor part is disposed on the inside of a cylinder, i.e., on the test subject side. This coil apparatus includes a conduction part for attaining conduction among the subcoils, and a conduction control part for controlling a conduction state between the first conductor part and the second conductor part, conducting connection to a transmission and reception part which conducts signal transmission and reception with a subcoil, and changing over electric capacitance of the subcoil according to whether to receive or transmit. Function changeover between the multi-channel mode and the one-channel mode is accomplished by conducting connection changeover and electric capacitance changeover.