This paper investigates one-way shear strength of slabs inserted with welded wire trusses and void spheres, which are effectively applied to the slabs through an experimental program. The maximum shear strengths of all specimens satisfy the nominal shear strength of the solid without shear reinforcements and void spheres. Generally, the shear resistance mechanism of a solid slab is supposed to occur with arch and beam action depending on the shear-span ratio. However, the mechanism of void slabs is developed in a different manner. The effect of arch action significantly decreases in the void slab, and as the shear-span ratio increases, the load-strain curves of lattice wires becoming increasingly disordered, which affects the shear strength. In addition, the shear failure of specimen rapidly occurred when the longitudinal reinforcements yielded. Based on the results, the shear force model of a void slab with lattice wires was proposed with the first shear crack force ratio and shear-span ratio.