To provide an optical fiber type sensor and an optical fiber type sensor system capable of measuring various variations of a measuring object in a wide measuring range and for a long term by using a hetero core type optical fiber easy to produce without applying excessive flexing or extension to the optical fiber.

This optical fiber sensor has the hetero core type optical fiber having a hetero core part; and a mechanism means converting stress into the flexing of the hetero core optical fiber round the hetero core part, and the loss of optical transmission is produced in the hetero core type optical fiber according to the flexing of the hetero core part. The optical fiber type sensor system has a fiber line for the hetero core type sensor formed by connecting in series one and more hetero core type optical fibers at the specified intervals; the mechanism means; a light incident means for making light for detection incident in the optical fiber line for the sensor; and a light receiving means receiving light for detection.