A side skirt mounting apparatus may include a side skirt that may be installed to be supported by a one-touch locker in an upper portion thereof and a hinge in a lower portion thereof, wherein the locker includes an upper bracket, a lower bracket, a skirt frame to which the upper bracket and the lower bracket may be engaged, a shaft installed to slidably penetrate the upper and lower brackets and to be selectively inserted into a hole formed to a side skirt bracket, and an elastic member mounted on an outer circumference of the shaft between the upper and lower brackets to elastically support the shaft.