This paper presents a model of frictional contact with soft tissue for the colonoscopy simulator with haptic fidelity. The colonoscopy simulator allows the user to navigate the three dimensional virtual colon constructed from CT (computer tomography) data of patients. The frictional contact model is proposed to integrate the therapeutic procedures such as polyp removal. The proposed model uses the finite element method based on the linear static elasticity to simulate deformation and reflective force including friction effects. The variation of the reflective force is computed according to the contact state, stick or slip state, during sliding contact motions. Simulation results show responses following the Coulomb's friction law.