Recently, Prestressed Reinforced Concrete (PRC) has been accepted as a reasonable structural member that permits cracking. A PRC member is a visible design alternative to either reinforced concrete (RC) or fully prestressed concrete (PC). In Japan, PRC has been widely used for bridge structures because it is economical. PRC members are generally designed to allow cracking under full service loads. Flexural cracking in PRC beams has been already studied and the flexural crack width can be accurately predicated by equations available in the present codes (ACI, CEB-FIP, JSCE, etc.). On the other hand, shear cracking behavior in PRC members is barely understood. The objective of the present study is, therefore, to experimentally explore the shear cracking behavior of PRC beams. Three I-shaped RC and four I-shaped PRC beams were tested under four-point monotonic loading. The experimental program was carried out focusing on the influence of prestressing force, side concrete cover, stirrup spacing, bond characteristics of stirrup and the amount of longitudinal reinforcement on shear crack width. The study revealed that the prestressing force significantly reduced shear crack width in PRC beams as compared to RC beams. In addition, an equation was proposed to calculate shear crack width in RC and PRC members. The proposed formula for shear crack width shows better correlation between calculated values and experimental data than the other formulae.