An object is to provide a shape measurement system and a shape measurement method that allow deriving a three-dimensional shape of a linear object to be measured over a long distance and with high resolution. A shape measurement system according to the present invention includes: a multi-core optical fiber (10) including a center core (11) arranged in a center of a cross section of the multi-core optical fiber (10) and three or more outer peripheral cores (12) arranged at equal intervals on an outside of the center core (11) and in a concentric manner; a measuring device (20) that measures a backward Brillouin scattering light distribution in a propagation direction of each core of the multi-core optical fiber (10); and an analysis device (30) that computes positional coordinates in a three-dimensional space of a linear structural object having an unknown three-dimensional shape from the backward Brillouin scattering light distribution of the multi-core optical fiber (10) arranged along the linear structural object having the unknown three-dimensional shape and the multi-core optical fiber (10) arranged along a linear structural object having an already-known three-dimensional shape.