The invention discloses a baseline-distance-variable scanning-type automobile topography detector based on a cubical pose datum. With the detector, automobile topography scanning can be realized by using a baseline-distance-variable cubical-pose-datum-based scanning way. The detector is composed of a cubical target (1), a T-shaped groove guiding rail (2), a laser casting instrument (3), a target inner camera (4), a target outer camera (5) and a tripod (6). The detector has advantages of small occupied space, simple structure, high checking accuracy, simple operation, easiness in installation, low cost, and reliable performance.