To calculate a high-resolution coil sensitivity distribution that does not depend on a shape or a structure of a subject with high accuracy. An MRI apparatus of the invention includes: a measurement unit that includes a reception coil including a plurality of channels, a measurement unit that measures a nuclear magnetic resonance signal of a subject for every channel of the reception coil; and an image computation unit that creates an image of the subject by using a sensitivity distribution for every channel of the reception coil, and a channel image obtained from the nuclear magnetic resonance signal measured by the measurement unit for every channel. The image computation unit includes a sensitivity distribution calculation unit that calculates a sensitivity distribution on a k-space for every channel by using the channel images and a composite image obtained by combining the channel images.