We report on epitaxial growth and magnetic properties of EuTiO 3 thin films with a perovskite structure. Single crystalline EuTiO 3 films with atomically flat surface are grown on ͑001͒ surface of SrTiO 3 by pulsed laser deposition ͑PLD͒ and subsequent annealing in reducing atmosphere. The as-deposited films possess the crystal structure with an elongated c-axis and tend to stabilize ferromagnetically ordered Eu 2+ spins at low temperatures. Postannealing at 1000°C relaxes the out-of-plane lattice strain, and brings about a drastic change in magnetic structure; the annealed film becomes an antiferromagnet below Néel temperature of 5.1 K. The change in magnetic properties accompanied by the modification in lattice constant is discussed.