In a visible light semiconductor laser with (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P (0.ltoreq.x .ltoreq.1) crystal layers and a process for growing an(Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P (0.ltoreq.x.ltoreq.1) crystal, a GaAs substrate on which (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P is grown in an epitaxial method selected from MOVPE and MBE provides one selected from a (110) plane, a plane equivalent to the (110) plane, a (111) plane, and a plane equivalent to the (111) plane as a main plane for a crystal growth of (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P. As a result, a bandgap energy Eg of the (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P crystal can be the maximum value inherent to the mixed crystal independent on a growth temperature and a V/III ratio.