A magnetic sensor includes an MR element and two bias magnetic field generation units. The two bias magnetic field generation units are spaced apart from each other along a first direction and configured to cooperate with each other to generate a bias magnetic field. Each bias magnetic field generation unit includes a ferromagnetic layer and an antiferromagnetic layer stacked along a second direction orthogonal to the first direction. An element placement region is formed between the two bias magnetic field generation units when viewed in the second direction in an imaginary plane perpendicular to the second direction and intersecting the MR element. The element placement region includes a middle region and two end regions. The MR element is placed to lie within the middle region in the imaginary plane.