To establish a method for executing works which can install facial materials (counter, bathtub apron, etc.) accurately in good compliance with the positional relationship between the sanitary equipment room space and bath tub etc.

Installation frames 1, 3 having the mounting parts for a counter (a) and bath tub apron (c) around a bath tub 100 are put in a compacted condition and carried into a sanitary equipment room X. The lengths of the mounting parts are internally adjusted as desired so that it meets the mating relationship with the sanitary equipment room space and bath tub 100 etc., and then the counter (a) and bath tub apron (c) are installed on the installation frames 1, 3.