To provide a controller and a control method for internal combustion engine which can calculate the shaft torque in unburning with good accuracy in all the operating condition in which calculation is required, using the shaft torque in unburning which was set in the specific operating condition, and can improve estimation accuracy of the parameter relevant to the combustion state. A controller for internal combustion engine calculates a specific shaft torque in unburning with reference to a specific unburning condition data; calculates specific and current generated torques of unburning assumption using the physical model equation; calculates a current shaft torque in unburning based on the specific shaft torque in unburning, and the specific and current generated torques of unburning assumption; and calculates an increment of gas pressure torque by burning based on the current shaft torque in unburning and the actual shaft torque in burning condition.