A method of arranging devices of a processing plant configured to process fluid, characterized by, the method comprising steps of: dividing a plurality of devices included in the processing plant into a plurality of device groups which are distinguishable from one another, and each include at least one device and each have set therefor an occupied area including an arrangement area for the at least one device, and setting, for the plurality of device groups, connection information representing that, in order to transfer the fluid between each device included in one device group and a counterpart device included in another device group, two specific device groups are connected and paired via a pipe, and pipe information required for calculating a use amount of a pipe material per unit length of the pipe corresponding to the connection information; setting an installation area of the processing plant, and a pipe-rack arrangement area having a band-like planar shape of a pipe rack (21, 22, 23) to be provided in the installation area to support the pipe; and repeatedly executing, by a computer, a first step and a second step while changing an arrangement of the plurality of device groups to obtain a plurality of arrangements, and selecting a plurality of arrangements having small total use amounts of the pipe materials from the obtained plurality of arrangements, the first step including arranging the plurality of device groups in the installation area so that an outer edge of the occupied area of the one device group is brought into contact with a long side of the pipe-rack arrangement area having the band-like planar shape and so that the occupied area of the one device group and the occupied area of another device group are prevented from overlapping each other, the second step including calculating, for the arrangement of the plurality of device groups, the total use amount of the pipe material of the pipe to be supported by the pipe rack (21, 22, 23) based on a position at which the outer edge of each occupied area is brought into contact with the long side and on the connection information, wherein the first step and the second step are repeated until an arrangement of the plurality of device groups having a total use amount of the pipe materials smaller than total use amounts of other arrangements is not able to be found. dividing a plurality of devices included in the processing plant into a plurality of device groups which are distinguishable from one another, and each include at least one device and each have set therefor an occupied area including an arrangement area for the at least one device, and setting, for the plurality of device groups, connection information representing that, in order to transfer the fluid between each device included in one device group and a counterpart device included in another device group, two specific device groups are connected and paired via a pipe, and pipe information required for calculating a use amount of a pipe material per unit length of the pipe corresponding to the connection information; setting an installation area of the processing plant, and a pipe-rack arrangement area having a band-like planar shape of a pipe rack (21, 22, 23) to be provided in the installation area to support the pipe; and repeatedly executing, by a computer, a first step and a second step while changing an arrangement of the plurality of device groups to obtain a plurality of arrangements, and selecting a plurality of arrangements having small total use amounts of the pipe materials from the obtained plurality of arrangements, the first step including arranging the plurality of device groups in the installation area so that an outer edge of the occupied area of the one device group is brought into contact with a long side of the pipe-rack arrangement area having the band-like planar shape and so that the occupied area of the one device group and the occupied area of another device group are prevented from overlapping each other, the second step including calculating, for the arrangement of the plurality of device groups, the total use amount of the pipe material of the pipe to be supported by the pipe rack (21, 22, 23) based on a position at which the outer edge of each occupied area is brought into contact with the long side and on the connection information, the first step including arranging the plurality of device groups in the installation area so that an outer edge of the occupied area of the one device group is brought into contact with a long side of the pipe-rack arrangement area having the band-like planar shape and so that the occupied area of the one device group and the occupied area of another device group are prevented from overlapping each other, the second step including calculating, for the arrangement of the plurality of device groups, the total use amount of the pipe material of the pipe to be supported by the pipe rack (21, 22, 23) based on a position at which the outer edge of each occupied area is brought into contact with the long side and on the connection information, wherein the first step and the second step are repeated until an arrangement of the plurality of device groups having a total use amount of the pipe materials smaller than total use amounts of other arrangements is not able to be found.