The use of water-insoluble polysaccharides (such as cellulose) as structural materials (referring to materials with macroscopic shapes in this chapter) has been practiced since ancient times; likewise, the use of water-soluble polysaccharides as structural materials has also been investigated. Not limited to polysaccharides, when aqueous solutions of anionic polymers and cationic polymers (both also called polyelectrolytes) are mixed, complexes (denoted as polyion complexes) are formed due to multiple electrostatic interactions between these oppositely charged polymers, most of which become insoluble in water. This phenomenon has been known for some time, and for example, porous structures obtained by freeze-drying polyion complexes composed of polysaccharides have been investigated for use as cell scaffolds. Furthermore, film materials have also been prepared by alternately laminating anionic polysaccharides and cationic polysaccharides in nm thickness using the layer-by-layer assembling technique, and the use of polysaccharide polyion complexes as film materials has attracted attention. Against such a background, a method has been reported in which dense films are obtained by molding polyion complexes composed of anionic polysaccharides such as chondroitin sulfate and cationic polysaccharide chitosan by hot pressing (Fig. 157.1) [1]. The obtained films (hereinafter referred to as polysaccharide composite films) are water-insoluble and free-standing and can be easily handled by hand. Various physical properties and functions of the films are also being evaluated, and it is expected to be used as a functional material and medical material.