Provided is a route planning system (KKS) having a plurality of moving bodies (IDT), a first moving body (IDT (1)) from among the plurality of moving bodies (IDT) including: a position acquisition unit (11) for acquiring the position of the first moving body (IDT (1)); a reception unit (3) for receiving routes (S2I, S5I) of second moving bodies (IDT (2), IDT (5)) from second moving bodies (IDT (2), IDT (5)) from among the plurality of moving bodies (IDT); and a route planning unit (12) for repeatedly planning one route (S1) for the first moving body (IDT (1)) on the basis of the acquired position of the first moving body (IDT (1)), evaluating the cost (δ1) of the planned one route (S1) for the first moving body (IDT (1)) using the received routes (S2I, S5I) of the second moving bodies (IDT (2), IDT (5)) and the planned one route (S1) for the first moving body (IDT (1)), and selecting another route (S1) for the first moving body (IDT (1)) that has a smaller cost (δ1) on the basis of the evaluated cost (δ1) of the one route (S1) for the first moving body (IDT (1)).