A magnetic sensor includes a substrate having a first surface and a second surface, which is opposite the first surface, and a detection unit provided on the first surface. The detection unit includes a magnetoresistive effect element, the resistance value of which changes in accordance with an input magnetic field, provided on the first surface, and a protective layer that covers at least the magnetoresistive effect element. The magnetoresistive effect element is configured in a linear shape extending in a first direction on the first surface. The detection unit has a first width, which is a length in a second direction, orthogonal to the first direction, and a second length, which is greater than the first width. The first width is the length of the detection unit on the first surface, and the second width is the length of the top surface of the detection unit.