A manufacturing method of filling a resin into a housing includes the steps of: providing a housing that has at least one recess, with the recess having first and second spaces, and the first space being disposed above the second space; inverting the housing; injecting a fluid into the recess to fill the first space, with the fluid having a viscosity coefficient and a surface tension less than those of water; and injecting a first resin into the recess, with the first resin having a specific gravity greater than that of the fluid, such that the first resin fills the first space and the fluid fills the second space.