[en] We report ac magnetic susceptibility and dc magnetization measurements on the superconducting ferromagnet UCoGe (with superconducting and Curie temperatures of T_SC-0.5 K and T_Curie-2.5 K, respectively). In the normal, ferromagnetic state (T_SC < T < T_Curie), the magnetization curve exhibits a hysteresis loop similar to that of a regular itinerant ferromagnet. Upon lowering the temperature below T_SC, the spontaneous magnetization is unchanged, but the hysteresis is markedly enhanced. Even deeply inside the superconducting state, ferromagnetism is not completely shielded, and there is no Meissner region, a magnetic field region of H < H_c1 (a lower critical field). From these results, we suggest that UCoGe is the first material in which ferromagnetism robustly survives in the superconducting state and a spontaneous vortex state without the Meissner state is realized. (author)