A field loading test on a natural slope was conducted in order to study suitable slope stability evaluation technique. Safety factors by Fellenius method and simplified Janbu's method were calculated based on the results obtained from the field loading test. The differences of the analysis and the relation between the displacement of the slope and the change of safety factor in each loading step were considered. The results are summarized as follows.
(1) The Fellenius method and the simplified Janbu's method gave the almost same value to the test slope.
(2) When safety factor by the Fellenius method decreased about 5% from the time that monitoring equipment detected dis-placement, the rate of displacement reached a steady state or had an acceleration tendency, which suggested that the slope changed into a limit equilibrium.