A sensor includes a film portion deformable by external force, a support body supporting the film portion, and a magnetoresistive element portion on the film portion and including a unit element that includes a first magnetic layer whose magnetization direction changes in accordance with deformation of the film portion, a second magnetic layer whose magnetization direction is fixed, and an intermediate layer between the first and second magnetic layers. The film portion includes a first side portion in a portion of an outer edge of the film portion. A slit portion is provided in the film portion and includes at least a portion along the first side portion, so that the film portion includes a connection portion in which the first side portion is partially connected to the support body. A magnetoresistive element portion is provided in the connection portion.