A manufacturing method of a resistive memory device includes the following steps. A first electrode is formed. A first metal oxide layer is formed on the first electrode, and the first metal oxide layer includes first metal atoms. A multilayer insulator structure is formed on the first metal oxide layer. A second metal oxide layer is formed on the multilayer insulator structure. The second metal oxide layer includes second metal atoms, the multilayer insulator structure includes third metal atoms, and each of the third metal atoms is identical to each of the second metal atoms. A second electrode is formed on the second metal oxide layer. The multilayer insulator structure is disposed between the first metal oxide layer and the second metal oxide layer in a vertical direction, and an atomic percent of the third metal atoms in the multilayer insulator structure changes in the vertical direction.