Characteristics of wave forces on a three dimensional body on a submerged breakwater have been investigated experimentally. Maximum wave force has been found to depend greatly on the location of the structure and its shape. In the vicinity of the leading crown edge, the plunging breaking occurs and the impulsive breaking wave force acts on it. The variation of the maximum wave forces are formulated based on Hiroi's and Goda's formulae. Moreover, the Morison equation has been modified to consider the varying water surface, and the calculated wave force using the velocity and acceleration at the front face is confirmed to reproduce well the experimental result. The numerical prediction method based on the VOF method has been also developed to estimate the velocity and acceleration of breaking waves on a submerged breakwater. With the use of these computed values and recommended drag and inertia coefficients, the Morison equation can give good estimation of wave force even in a case that the impulsive breaking wave force acts on the structure.