Punching shear capacity of deteriorated reinforced concrete slab is experimentally investigated in this study. Since horizontal crack near the upper side rebar is often observed in deteriorated reinforced concrete bridge deck slabs due to rebar corrosion, horizontal crack propagation behavior was investigated by accelerated electric corrosion test. Then, in order to evaluate the influence of the horizontal crack on punching shear capacity of slabs, loading tests were carried out using the test specimens with the corrosion‐induced crack and with an artificial horizontal crack. According to the test results, the horizontal crack near the upper side rebar has a significant impact on punching shear capacity of slabs, and it is confirmed that punching shear capacity of reinforced concrete slab correlates to the width of the horizontal crack. Also, it is revealed that cover concrete above horizontal crack does not effectively work if width of the horizontal crack grows to a certain amount.