A magnetic sensor device having a spin-valve-type magnetoresistive effect element and capable of stably applying a bias magnetic field on the free layer of the magnetoresistive effect element includes a spin-valve-type magnetoresistive effect element, a substrate on which the magnetoresistive effect element is positioned, a power source that supplies a substantially constant electric current applied on the magnetoresistive effect element, and a magnetic field generator that is connected to the electric current path of the electric current applied on the magnetoresistive effect element in series. The magnetic field generator is provided to be capable of applying a bias magnetic field on at least a portion of the magnetoresistive effect element. The magnetic field generator is close to a portion of the magnetoresistive effect element and is positioned at a different level from the substrate.