E-stir is established as a technology development company based on Stirling Engine on April 25, 2005. Its aim is to save energy using home-use cogeneration, waste heat and biomass utilization. We started a fundamental study of a high performance Stirling Engine. Especially we have been studying a free-piston Stirling Engine (FESP) with a linear alternator to be able to realize its compact design and high efficiency. In order to achieve these expected characteristics, it is important to develop a compact and high efficiency linear alternator for composing FESP. Therefore, we are now proposing a new type of linear alternator using quality engineering skill and magnetic field analysis.