This volume is a collection of papers from the fourth meeting of the International Symposium on Mesoscopic Superconductivity and Spintronics held at NTT Atsugi, Japan. Research in these fields has advanced a great deal since the previous meeting, largely because these fields have drawn much attention from the viewpoint of new quantum phenomena and quantum information technology. Mesoscopic superconductivity has been developed in new fields, such as a ferromagnet/superconductor junction, the proximity effect in unconventional superconductors, macroscopic quantum tunneling in high-Tc superconductors, quantum modulation of superconducting junctions and superconducting quantum bits. This book also covers transport and spins in nano-scale semiconductor structures such as quantum dots and wires, quantum interference and coherence and order in exotic materials, and some papers on quantum algorithm. This book adequately provides an overview of recent progress in mesoscopic superconductivity.