A tape run control unit in a magnetic recording and reproducing apparatus is provided with a discriminator and on a controller. The discriminator detects a stand-by time until a signal to be recorded is received in repositioning of the tape and generates a discrimination signal for discriminating the length of the stand-by time. The controller controls tape driving unit such as a capstan motor during the reposition and controls the stop position of the tape such that a magnetic head scans the portion of the tape where no data is recorded. After completion of repositioning, furthermore, the controller is responsive to a discrimination signal so as to select the stop mode which involves the release of pinch roller when the stand-by time is long and to select the mode for simply stopping only the capstan when the stand-by time is short.