To provide an optical differential pressure measuring method and an optical differential pressure sensor having large sensitivity to fine pressure variation and capable of precisely measuring the fine pressure variation on a surface of an object.

The optical differential pressure measurement is achieved, which is constituted of a porous partition wall 1 having fine flow passages and an oxygen-sensitive surface 2 to which an oxygen quenching dye is attached, wherein gases with different oxygen concentrations flow out through the fine flow passages in the porous partition wall 1 according to the differential pressure generated across the porous partition wall 1, and large variation in oxygen concentration is generated on the oxygen-sensitive surface 2. By utilizing the generated large variation in oxygen concentration, the optical differential pressure measurement with very high sensitivity is achieved, in which the variation in the light emission intensity or light emission life of the oxygen quenching dye is larger than that of the conventional one.