The intelligent operating theater (IOT) is an operating room where it provided with "Advanced hands, vision and brain for Surgeon". Improvement of the surgical outcome of malignant brain tumor surgery requires a better anticipation of the surgical procedure and patient's anatomical and functional environment of the region of interest (ROI). Localization of functional areas in the brain also differs among patients, and excess removal of tumor near eloquent areas may increase the risk of damage to function, such as motor paresis and speech disturbance. Recent progress in magnetic resonance (MR) imaging technology which enabled to acquire intraoperative images totally changed the neurosurgery of malignant brain tumor. Since intraoperative MR images (iMRI) visualize the size of residual tumor and the positional relationship between the tumor and eloquent areas, surgeons can achieve safe and reliable surgery. The IOT with iMRI has a role to assist the surgeon's decision for next surgical procedures by showing the present status real-timely. In order to compensate the deformation and shift of the organ due to surgical procedures preoperative images are not sufficient and it is necessary to up-date the navigation information using intraoperatively acquired images. These surgical support using intraoperative images are a must to accomplish the safe and accurate surgery.