To provide a new photo-crosslining polysaccaride having a low swelling property and high biodegrading property while maintaining a certain degree of strength.

In a polysaccaride pseudo-sponge obtained by a method wherein a polysaccaride gel having a shape-keeping property is obtained by irradiating a solution of photoreactive polysaccharide wherein a photoreactive group is introduced to the polysaccharide with light, then the polysaccaride gel is freezed or freezed-dried, then the obtained freezed polysaccaride gel or freezed dried body is irradiated with light, and also the polysaccaride is any given in the following (a) and the photoreactive group is any given in the following (b), (a) polysaccaride is hyaluronic acid, alginic acid or carboxymethyl cellulose, (b) photoreactive group is either residual group selected from a group of cinnamic acid, substituted cinnamic acid, acrylic acid, maleic acid, fumaric acid, furil acrylic acid, thiophene acrylic acid, cinnamylidene acetic acid, sorbic acid, thymine and coumarin.