Biosensor and biochip

A biosensor for detecting a biomolecule in a sample, the biosensor comprising:

• a substrate having a surface in which a first region and a second region disposed adjacent to the first region are formed;
• a magnetoresistance effect element that is disposed on the first region and is configured for a detected resistance value to be changed based on an input magnetic field;
• a soft magnetic thin film that is disposed on the second region;
• a protective film that is disposed on both the first region and the second region, covers a surface of the soft magnetic thin film, and is disposed on the top part of the second region and contains an affinity substance capable of recognizing the biomolecule on the outer surface of the second region exclusively;
• and
• an MR cover film that is disposed on at least the top part of the first region and is disposed on the protective film above the magnetoresistance effect element, and is substantially free of the affinity substance,
• wherein the soft magnetic thin film is configured to transmit a component in the in-plane direction of the laminate of a stray magnetic field of magnetic beads accumulated on the soft magnetic thin film to the magnetoresistance effect element,
• the protective film and the MR cover film are made of different materials,
• the protective film is composed of a plurality of films, and
• the MR cover film is disposed on either of the first region and the second region on a film other than the top film among the plurality of films constituting the protective film.