A photocurable hyaluronic acid derivative of the present invention comprises hyaluronic acid and a photoreactive crosslinking group bonded thereto, wherein a 1.0 wt. % aqueous solution of the photocurable hyaluronic acid derivative obtained by dissolving the solid photocurable hyaluronic acid derivative in an aqueous solvent, is capable of passing through a porous filter having a pore size of 0.45 .mu.m and a diameter of 25 mm at a rate of not less than 2 ml/minute at 24.degree. C. under a pressure of 5.0 Kg/cm.sup.2 ; and a process for producing the photocurable hyaluronic acid derivative; and a photocured crosslinked-hyaluronic acid derivative; a medical material using the photoreactive hyaluronic acid derivative and a medical material using the photocured crosslinked-hyaluronic acid derivative.