To provide an optical fiber sensor capable of measurement rapidly by using a wavelength dispersion type spectrograph.

The optical fiber sensor 1 includes a sensor system 10 for applying incoherent light comprising a white light source 5 to a diaphragm sensor section 3 via a coupler 4; the wavelength dispersion type spectrograph 30 in which return light from the diaphragm sensor section 3 enters via the coupler 4; and a signal processing system 40 in which a return light signal is inputted. In the optical fiber sensor 1, one of pressure, force, temperature, and flow rate from the return light signal to the diaphragm sensor section 3 is measured. When an A/D converter 42 for converting the return light signal to a digital signal and a D/A converter 43 for displaying a pressure value are connected to an electronic computer 41 by a serial or parallel interface, pressure and force can be measured speedily with high resolution.