The present disclosure provides a grid fixing apparatus including a spacer-integrated retaining clip and a grid fixing method using the same capable of integrally forming a retaining clip and a spacer, forming a grid fixing apparatus to be tacked into an object through an anchor pin to firmly fix a grid reinforcement material to a surface or an outer side of the object, and fixing the grid reinforcement material in vertical and horizontal directions to precisely construct the grid reinforcement material and capable of being applied to all grid reinforcement materials manufactured in a lattice shape, such as a metallic mesh, a geogrid, and a textile grid made of a high-strength fiber, and being utilized in construction of a grid reinforcement material to which various binders such as concrete, mortar, a pavement material, and a finishing material are applied.