PURPOSE: To provide a sensor film for optical sensor for measuring O2, H2O2, SO2 or hydrocarbon halide in a sample.

CONSTITUTION: An indicator material uniformly fixed into the polymer matrix of a sensor film, which is at least indirectly in contact with a sample, and has optical properties at least one of which is changed when a parameter to be measured is changed, contains an inorganic salt of transition metal complex having α-diimine ligand. This indicator material is uniformly dispersed in a polymer matrix formed of at least one material selected from the group consisting of cellulose derivative, polystyrene, polytetrahydrofuran, and its derivative.