As the first step to clarify the grinding mechanism of FRP, the quality of ground surface finish of unidirectional glass fiber reinforced plastics was investigated. It was shown in the previous paper [1] that the aspects of the cut end of glass yarn near the ground surface were classified into two modes by the direction of glass yarn, such as, the hollow pit and the swollen proturberance (uncut glass yarn). The present paper describes the investigation on how to produce the same quality ground surface finish irrespective of the change of glass yarn direction in the specimen and how the grinding method affects the quality of ground surface finish.The following results were obtained.(1) It was difficult to achieve the same quality of ground surface finish when the glass yarn direction was changed.(2) On the spark-out grinding, the length of uncut glass yarn decreased with increasing the number of spark-out grinding.(3) On the orthogonal plunge cut grinding, the length of uncut glass yarn increased with increasing the number of plunge cut.(4) None of these grinding methods could reduced the depthe of hollow pits.