Working plan assistance device and working plan assistance method

A working plan assistance device, comprising:

• a server and a terminal comprising circuitry configured to cause an output interface to output a working plan assistance image in which respective occupation modes of an upper structure of a crane and a modeled building in each of a plurality of designated planes spaced apart from each other are displayed, the plurality of designated planes constituting a designated plane group defined in a front-rear direction of the upper structure, the designated plane group being perpendicular to a width direction of an attachment of the crane, the attachment being configured to derrick relative to the upper structure, the upper structure being revolvable around a revolution axis line extending in a vertical direction to a lower structure in the crane which is modeled in a three-dimensional virtual space, wherein
• a posture of the designated plane group changes according to a revolution of the upper structure such that a precision of estimation of interference between the upper structure of the crane and the building is improved based on the respective occupation modes of the upper structure and the building in the plurality of designated planes.