PROBLEM TO BE SOLVED: To provide a growth unit capable of preventing a growing environment of shellfish such as a sand-submerged bivalve from being deteriorated.SOLUTION: In a growth unit 1 of shellfish which is used on a tideland, and which is separated from the outside world by covering the upper part of the sea bottom 6 with an upper covering net 2, spacer means 3 is installed so as to form a space 7 between the upper covering net 2 and the sea bottom 6.