The differential thermal analysis (DTA) apparatus has been developed for a commercial superconducting magnet. The DTA apparatus could detect the kinetics and thermodynamics of phase transformation with and without a magnetic field. Preliminary results for Al-Al2Cu eutectics are presented. The DTA curves indicate the similarity at several rates regardless of a magnetic field; however, at the same rate, melting transformation seems not to be influenced by a magnetic field, while solidification could be delayed via suppressing nucleation and crystal growth in a magnetic field. It will be believed that the DTA apparatus can be used to investigate the phase transformation of substances of interest in a magnetic field.