To provide a driving behavior intention detector capable of reliably detecting the driving intention of a driver and excellent in detection performance.

The sight line direction data E (θu, θv) is calculated by an image processing unit 25 from the data by a CCD camera 21 and an infrared ray irradiation unit 23. An electronic control unit 31 calculates the sight line direction frequency distribution F from the sight line direction data E (θu, θv). Driving control input, vehicle behavior data and environment information are input in the electronic control unit 31 from a driving control input input unit 43, a vehicle behavior data input unit 45, and an environment information data input unit. By using the imbedded Markov model, the parameter of driving behavior model λi is estimated, and stored in a driving parameter storage unit 41. The driving behavior intention is estimated based on the measured observation data and the parameter of the driving behavior model λi.