Variation of the surface coastal current in the marginal sea off the west coast of Sumatra during the Pre-YMC and YMC periods was investigated by the R/V “Mirai” cruises (Pre-YMC [Years of the Maritime Continent]: MR15-04 and YMC: MR17-08). One of the major differences between the cruises of MR15-04 and MR17-08 was the direction of the surface coastal current. According to the LADCP observation, the southeastward current along the coast was continuously dominant under the forcing of a weak easterly winds in the MR15-04, whereas in the MR17-08, the current direction was rotated counterclockwise around 10 days under the strong westerly wind forcing after the passage of the MJO, suggesting the passage of meso-vortices. The difference was confirmed by the oceanic reanalysis of the ECCO2, and it was confirmed that the meso-vortex was slowly moved along the coast (about 300 km / 10 days). It was suggested that the presence or absence of the meso-vortex formation caused a large difference in not only the horizontal advection but also the up or down welling in the mixed layer. The meso-vortex was also accompanied by a clear maximum of the sea surface height, and a large vertical motion in the mixed layer is estimated in ECCO2. The coastal meso-vortex was gradually formed and developed under the continuous westerly wind forcing more than 10 days after the MJO passage.