A signal processing apparatus including a first position calculation unit that calculates a three-dimensional position of a target on a first coordinate system from a stereo image captured by a stereo camera, a second position calculation unit that calculates a three-dimensional position of the target on a second coordinate system from a sensor signal of a sensor capable of obtaining position information of at least one of a lateral direction and a longitudinal direction and position information of a depth direction, a correspondence detection unit that detects a correspondence relationship between the target on the first coordinate system and the target on the second coordinate system, and a positional relationship information estimating unit that estimates positional relationship information of the first coordinate system and the second coordinate system on the basis of the detected correspondence relationship.