The present paper describes a method finding bead shapes in shell structure to decrease the absolute value of mean compliance under periodic loading by using a solution to shape optimization method. Variation of the shell structure in out-of-plane direction is chosen as a design variable. To create beads, the out-of-plane variation is restricted by using the sigmoid function. The integrated absolute value of mean compliance in target frequency range is used as objective function. An iterative algorithm based on the $H^1$ gradient method is used to solve the problem. The effectiveness of the method is confirmed by numerical example.