T. Ikawa obtained the following differential equation D(subscript T)D(subscript T)D(subscript T)T-KD(subscript T)T, K=κ^2-T^2 for the clrcular helix which corresponds the case that the curvature κ and torsion (The symbol is abbreviated) of timelike curve α on the Lorentzian manifold M1 are constant [5]. In this paper, we have defined a slant helix according to Bishop frame of the timelike curve. Furthermore, we have given some necessary and sufficent conditions for the slant helix and T. Ikawa's result is generalized to the case of the general slant helix.