1. A magnetic resonance imaging system comprising: static field generating means for generating a static field to be applied to a head of a human forming an object to be examined; gradient field generating means for generating a gradient field to be applied to the head of the human object; radio-frequency field transmitting means for transmitting a radio-frequency field to be applied to the head of the human object; receiving means for receiving a radio-frequency magnetic resonance signal from the head of the human object; sequence control means for driving said gradient field generating means, said radio-frequency field transmitting means and said receiving means in accordance with a predetermined sequence while the static field is applied from said static field generating means to the head of the human object, thereby applying the gradient field and the radio-frequency field to the head of the human object at a predetermined timing, and causing a predetermined magnetic resonance phenomenon in the head of the human object; signal processing means for performing predetermined processing of magnetic resonance signal data generated as a result of an operation of said sequence control means and received through said receiving means so as to obtain a magnetic resonance image; and display means for displaying the image obtained by said signal processing means, wherein said receiving means comprises head coil means for receiving the magnetic resonance signal, said sequence control means comprising multi-slice control means for executing a multi-slice method using a sequence with a relatively long echo time so that a magnetic resonance signal of a proton of fat is suppressed and a magnetic resonance signal of a proton of cerebrospinal fluid is emphasized, and said signal processing means comprises weighting summation processing means including means for setting a weighting coefficient to be smaller for a slice at a deeper position as compared to a more shallow position in order to produce weighted multi-slice images and means for summing said weighted multi-slice images so as to produce an image of a brain surface of the head.