We have grown pseudomorphic Tm 3Fe 5O 12 films (46-350 nm in thickness) with perpendicular magnetization on (111) Gd 3Ga 5O 12 substrates. Among various garnets, Tm 3Fe 5O 12 is selected because of a negatively large magnetostriction constant to overcome strong shape anisotropy in very thin films. A stress-induced anisotropy field as large as +25 kOe is estimated by calculation under a moderate in-plane tensile strain of +0.49%. The magnetization hysteresis loop and magnetic domain structure indicate the perpendicular easy axis. The domain size (W) in its maze pattern varies from 500 to 960nm with increasing thickness (t) and agrees well with a scaling law of W ∞ √t.