A solar cell 1 has a number of grooves 2 formed in parallel with each other on a first main surface 24a of a silicon single crystal substrate. An electrode 6 is formed on the inner side face of each groove 2 on one side. Each groove 2 is formed in the direction in disagreement with the <110> direction on the first main surface 24a. This raises mechanical strength of the solar cell 1. The direction of formation of the grooves 2 preferably crosses the <110> direction nearest to the direction of formation at an angle of 4.degree..about.45.degree. on the acute angle side.