In this paper, we define a ruled surface obtained by an infinitesimal bending of a curve in Minkowski [Formula: see text]-space. We also characterize such ruled surfaces according to causal characters of the curve. Furthermore, we find appropriate conditions of ruled surfaces obtained by infinitesimal bendings of curves to be (lightlike) developable, in particular, cylindrical or conical in Minkowski [Formula: see text]-space, with examples presented.