In this paper, the contouring control problem for the 5 DoF dual-arm robot manipulators with constraints is studied. The method of equivalent errors, previously proposed for unconstrained motion systems, is generalized to the system with holonomic constraints in which Lagrange approach is taken. It is demonstrated that the proposed method can be applied to the constrained system provided that the constraints satisfy a proper condition. The contouring controller design is dealt with the problem of stabilization obtained by equivalent errors. Experimental results for contouring paths with different feed-rate verify the effectiveness of the proposed method.