A three-dimensional shape measuring device is provided that enables an accuracy in measuring a three-dimensional shape of a subject to be improved even when a relationship between a luminance value and a distance deviates from an ideal point light source model in which the luminance value is inversely proportional to the square of the distance. A biometric authentication device includes a coefficient setting unit that sets a coefficient that is an index of a power in a model expression for making a luminance value of a captured image be proportional to an inverse of the power of a distance from a light source to a measurement point of the luminance value according to a prescribed condition, and a three-dimensional shape measuring unit that measures the three-dimensional shape of the subject according to the luminance value of the captured image and the coefficient.