The development of a sand spit and a sandbar along the north shore of Lake Yamanaka was investigated using satellite images together with measurements of the shoreline configuration and longitudinal profiles using an RTK-GPS. Sampling of the shore material was also carried out. In this lake, a sand spit and a sandbar have developed along the north shore because of the effect of wind waves. Near the east sand spit, waves generated by strong wind are obliquely incident in the direction normal to the shoreline along the south side of the sand spit, causing longshore sand transport toward the tip of the sand spit, whereas waves are obliquely incident at a large angle of over 45° in the direction normal to the shoreline around the northeast end of the sand spit, resulting in high-angle wave instability. Similarly, wind waves are obliquely incident at a large angle of over 45° at the west sandbar, satisfying the condition of high-angle wave instability. It was concluded that the shoreline configuration along the north shore of Lake Yamanaka has been strongly governed by wind waves.