To provide a package structure for securing a satisfactory optical coupling between an optical device arranged beforehand on a printed board and an optical device newly mounted on the particular printed board. The process of heat induced antigen recovery and the process of staining the biological sample on the microscope slide are conducted in the same apparatus, wherein the microscope slides do not need to be physically removed from one apparatus to another. Cylindrical portions of the outer electrode, the dielectric intermediate layer and the inner electrode have front ends situated in a plane of the front face of the wafer. The resistor cable is disposed in the rack for corresponding to each storage space.