PURPOSE: To eliminate flatness measurement in advance by leveling the seatings on the floor, which correspond to the two, right and left, setting and installing positions of a cabinet and installing and fixing other installing and fixing positions on the floor without clearance after supporting the cabinet on these seatings.

CONSTITUTION: In order to install and fix a cabinet 9, first of all, the seatings 81 to 84 on the floor, which correspond to setting and fixing positions 91 to 94 of both the right and left ends of the cabinet 9, for example, respectively, are leveled. In the next step, the cabinet 9 is installed on the seatings 81 to 84 and is fixed to and supported by only the setting and installing positions 91 to 94. Then, according to the deflection of the cabinet 9 due to supporting and fixing, other setting and fixing positions 71 to 74 are installed and fixed on the floor without clearance. Or, other seatings 85 and 86 on the floor, which correspond to setting and fixing positions 95 and 96 of two positions in the center part of the cabinet 9, for example, respectively, are leveled and also fixed. While confirming the prependicularity of the cabinet 9, the other setting and installing positions 75 to 78 are installed and fixed on the floor without clearance according to the deflection of the cabinet 9.