In the title compound, C(15)H(14)N(2)O(5)S(2)·CH(4)O, the six-membered ring fused to the β-lactam unit adopts a twisted conformation. In the crystal structure, the component mol-ecules are linked into a three-dimensional framework through inter-molecular N-H⋯S, N-H⋯O and O-H⋯O hydrogen bonds and C-H⋯O contacts.