The medaka (Oryzias latipes) is an excellent vertebrate model for studying the development of the retina. Its genome database is complete, and the number of opsin genes is relatively small compared to zebrafish. Short wavelength sensitive 2 (sws2), a G-protein-coupled receptor expressed in the retina, has been lost in mammals, but its role in eye development in fish is still poorly understood. In this study, we established asws2aandsws2bknockout medaka model by CRISPR/Cas9 technology. We discovered that medakasws2aandsws2bare mainly expressed in the eyes and may be regulated by growth differentiation factor 6a (gdf6a). Compared with the WT,sws2a−/−andsws2b−/−mutant larvae displayed an increase in swimming speed during the changes from light to dark. We also observed thatsws2a−/−andsws2b−/−larvae both swam faster than WT in the first 10 s of the 2 min light period. The enhanced vision-guided behavior insws2a−/−andsws2b−/−medaka larvae may be related to the upregulation of phototransduction-related genes. Additionally, we also found thatsws2baffects the expression of eye development genes, whilesws2ais unaffected. Together, these findings indicate thatsws2aandsws2bknockouts increase vision-guided behavior and phototransduction, but on the other hand,sws2bplays an important role in regulating eye development genes. This study provides data for further understanding of the role ofsws2aandsws2bin medaka retina development.