A magnetic sensor device comprises a magnetic sensor chip that has a substantially rectangular shape and that contains a magnetic sensor element; and a sealing body, which is composed of a resin material containing magnetic particles and that integrally seals the chip. The chip includes a first and second side surfaces which are mutually opposite to each other, and a third and fourth side surfaces which are mutually opposite to each other and orthogonal to the first and second side surfaces. The sealing body contains first to forth sealing parts. The thicknesses of the first and second sealing parts are smaller than the particle diameter of the particles, and the thickness of at least the third sealing part is larger than the particle diameter of the particles. The particles exist in at least the third sealing part and substantially do not exist in the first and second sealing parts.