A blood sample contained in a sample container is separated into a serum and a clot by a separating medium. An apparatus for sensing the blood sample includes a first sensing unit which senses the separating medium using an infrared sensor and outputs a first sensing signal, a second sensing unit which senses the serum and the clot using an infrared sensor and outputs a second sensing signal, a driving unit which moves the first sensing unit and the second sensing unit relative to the sample container, a position sensing unit which outputs a position sensing signal indicating a position of the first sensing unit and a position of the second sensing unit, and a controller which calculates positions of the separating medium, the serum and the clot in response to the first sensing signal, the second sensing signal and the position sensing signal.