The hydrodynamic effects of the angles of the intersection between hull-side and the freesurface, so-called the Wedge-effects are investigated in the two-dimensional radiation and diffraction problems. First and second-order forces by the regular perturbation theory are calculated for two bodies which have the same beam/draft ratio and the sectional area, one intersects at right angles at free-surface, and the other does at a half of right angles. Experiments in forced heaving and swaying oscillations and the diffraction problem are carried out and compared with the calculations. Obtained results summarize as follows. 1) First-order hydrodynamic coefficients are not affected very much by the Wedge-effects to the extent of a half of right angles. 2) Second-order vertical forces are affected significantly by the Wedge-effects, but horizontal forces are affected little. 3) The Wedge-effects can be explained as the oscillatory change of wetted-surface and the experimental results agree well with the calculations.