A procedure to retract brain tissue is a fundamental and important procedure for accessing a lesioned part located in the deep brain in neurosurgery. In order to provide a training environment to novice surgeons, a prototype of a surgical simulator which can simulate the retraction of soft tissue utilizing the advantage of an encountered-type haptic interface using MR fluid has been developed. In this paper, a force controller for displaying a retracting force of soft biological tissue with a spatula is proposed. The haptic interface was connected with a simple FEM (Finite Element Method) based simulator and displayed the computed reaction force from virtual tissue by using the proposed controller.