A parallel imaging (PI) method has been frequently used as a method for shortening an image acquisition time in the MRI field. The PI technique is a method for acquiring data using multi-channel coils, that is, several coils, when acquiring the data in MRI. According to this technique, data, the amount of which is smaller than that when the data is obtained using only one coil, is acquired, and then an image is obtained using coil information. According to an embodiment, a new image reconstruction method is proposed which adopts an expectation maximization (EM) technique that is different from the existing GRAPPA or SENSE technique when an image is obtained using PI data acquired through the radial trajectory.