A non-projected and sandglass-shaped bolt called a Double Spindle Fastener has been developed to prevent corrosion, comprising a countersunk head bolt and countersunk sleeve nut. This study conducted double shear tests of DSF with a compression-type jig to investigate the relationship among the shear plane location, failure modes, and maximum load. Shear tests of 10.9Class-M22 hexagonal head bolts, commonly used in steel bridges, were also conducted to compare their shear failure resistances and to clarify how to improve them. DSF’s maximum load was increased as the number of engaged threads while being lower than that of the 10.9Class-M22 bolt. Compared to designed resistances, DSF’s maximum load was higher than those of 10.9Class-M20 and 8.8Class-M22 bolts and exceeded sufficiently that of 14.9Class-M16 bolts. Thus, a composite section of countersunk bolt and sleeve nut was found functional, and they resisted the applied shear force together as number of engaged threads increased like with a long-type bolt and nut.