A perfobond rib is a steel plate with openings and acts as a shear connector in the concrete by a concrete dowel effect. It is realized that the perfobond rib shear connector would reach split failure at ultimate under low confinement and low shear strength, but the shear strength will be improved by enough confinement against split failure. In this paper, the shear strength of perfobond rib is examined by two series of experiments which are active confinement tests using hydraulic actuator and passive confinement tests using reinforcing bars. The test results indicate that the shear strength would be able to improved by giving confinement stress and the evaluation of shear strength under confinement is proposed.