The reading circuit of output signals from a plurality of magnetic detection elements is simplified and the reading resolution of a magnetic pattern is improved. A magnetic sensor device includes a magnetic detection element (11), and a magnet (13) applying a bias magnetic field to the magnetic detection elements (11) with a line of magnetic force in the constant direction. The magnetic sensor device detects a magnetic field change when a medium with a magnetic pattern passes through the bias magnetic field as an electric signal through the magnetic detection elements and reads the magnetic pattern of the medium. A plurality of the magnetic detection elements (11) is arrayed along a line intersecting the relative movement direction of the medium. A plurality of reading switches (22) is connected to the respective magnetic detection elements (11) and an output line (28) common to the plurality of magnetic detection elements (11). The magnetic sensor device includes a shift register (23) closing the reading switches (22) sequentially one by one to transfer the outputs from the magnetic detection elements (11) sequentially one by one to the output line (28).
