The method of Gutzwiller is extended to include antiferromagnetism in a s-band Hubbard model. A first-order paramagnetic (PM) to antiferromagnetic (AFM) transition is obtained with increasing UW ratio. The AFM ground state in the phase diagram is restricted between the electron density n1<1 and n2=2-n1. It is also bounded from below by a critical value of UW. The complete AFM ordering appears only for n=1. As n approaches n1 or n2 along the phase boundary, the AFM ordering gradually disappears. The AFM ordering is essentially due to virtual electron hopping, and the values of n1, n2, and critical UW depend on the bare density of states and the coordination number. The probability of having antiparallel-spin nearest-neighbor pair is computed. The result is consistent with the phase diagram. We also found a region in the phase diagram where the PM and the AFM states coexist. The AFM ground state at n=1 is insulating. Depending on the value of UW, the present theory predicts either an AFM insulating --> PM metallic or an AFM insulating --> PM insulating --> PM metallic transition as the temperature is raised. Therefore, the V2O3-type phase diagram follows from the present theory.