Wave forces exciting springing of ships are investigated theoretically and experimentally in relation to ship-side waves herein. Ship-side waves around a ship with zero forward velocity in regular waves are calculated by applying the finite element method extended on the basis of Chen and Mei's theory for long waves, assuming that the effect of ship's bottoms can be disregarded in case of springing. Ship-side waves thus calculated become very large near the bow part compared with the incident wave, and go along the ship with the same velocity changing the amplitude which can be regarded as a point function. With the use of the ship-side wave pattern obtained, the bottom pressure of ship is calculated on the basis of the strip theory, and the results are compared with the experments performed with a wooden model of rectangular cross sections. In the frame work of the linearized theory, only resonace of the first order appears, and resonance of the higher order is presumably caused by the nonlinearity of water pressure caused at the bow parts. This conclusion is completely different from Kurnai's, which is based on the frequency modulated ship-side waves.