We experimentally investigate (1) superconductivity which results in the disappearance of electrical resistance in certain materials, and superfluidity which leads to the viscosity of liquid helium vanishing, (2) magnetism of molecules and rare-earth compounds, (3) competing or coexisting phenomenon between superconductivity and magnetism. One of the subjects we are now concentrating on is the Josephson effect that enables zero-resistance current to flow through a normal metal inserted between two superconductors. This occurs by the quantum mechanical property of superconductivity and becomes remarkable at very low temperatures. Quantum mechanical world that appears at low temperature is our main research subject.