A waterproofing agent composition comprises 100 parts by weight of the pine resin, 20 to 70 parts by weight of an expanded styrene resin, 1 to 10 parts by weight of a vinyl-based resin and 100 to 750 parts by weight of an organic solvent. The waterproofing agent composition is a liquid and exhibits superior adhesion to various materials, thus providing proofing characteristics, humidity resistance and permeability resistance to surfaces of various materials water. In addition, the waterproofing agent composition may provide heat insulation characteristics along with waterproofing characteristics, humidity resistance and permeability resistance to subjects or bases, thus being used for various purposes.