We study pitchfork bifurcations and linear stability of solitary waves in coupled nonlinear Schr\"odinger equations on the line. The coupled equations possess a solution of which one component represents a solitary wave to a single equation and other is zero. We call the solution a fundamental solitary wave. It is known that pitchfork bifurcations of the fundamental solitary waves occur successively. We utilize the Evans function approach to determine the linear stability of bifurcated solitary waves. This is a joint work with K. Yagasaki.