A cruise control device and an obstacle detection device are provided which achieve a safe and appropriate tracking control by avoiding a sudden recognition of a short following distance when a preceding vehicle is found in an uphill or downhill gradient, in a curve, or at an intersection, or by reducing the damage of a crash when the crash cannot be avoided. An obstacle determination process section is provided which receives information from a sensor which detects an obstacle, receives terrain information of the position of the host vehicle from a navigation device, and determines the presence of the obstacle when a predetermined condition is satisfied after the sensor detects the obstacle. The predetermined condition to determine the presence of the obstacle is changed based on the terrain information of the position of the host vehicle received from the navigation device.