The Philippine Sea is one of the biggest marginal seas with the basins whose evolutions are interpreted in terms of trapped basin, backarc spreading basin and so on. Magnetic anomaly lineations in the basins play the critical role for the study of these evolutions. However there is not unique interpretation of magnetic anomaly lineations especially in the West Philippine Basin where the most important problem whether spreading is of one-limb or two-limb is still conserved. In the Shikoku Basin the detailed investigations carried out through the Continental Shelf Survey Project of the Hydrographic Department of Maritime Safety Agency of Japan provided the confirmative data by which the two-limb symmetrical spreading associated with displacement and rotation of segments of magnetic anomaly lineations was concluded as the most possible mode of evolution. There is no definite magnetic anomaly lineation found in the Parece Vela Basin due to a poor anomaly signature and rather sparse measurements which also conserves the problem if the Parece Vela Basin and the Shikoku Basin were formed as one backarc spreading basin.