We propose an SDN-based adaptive worst-fit multipath routing (AWMR) algorithm for Data Center Networks (DCNs) which can select multiple routing paths and determine the number of paths used for a new-coming flow according to the available network resources and the demanded bandwidth of the new-coming flow, instead of using a fixed number of routing paths for each flow. The proposed AWMR is composed of two stages. The first stage of the proposed AWMR finds an initial routing path set that includes paths whose lengths are the shortest between source and destination hosts, and computes available bandwidth of such a path set. The second stage of the proposed AWMR, which utilizes an improved widest disjoint path (iwdp) scheme, then selects the worst-fit paths according to the demanded bandwidth of the new-coming flow. Since the proposed AWMR minimizes the number of routing paths used effectively, the cost of constructing multiple paths can be decreased. Since the proposed AWMR selects multiple paths in a global view rather than in a local view of DFS+worst-fit-link, which is a representative related work, the proposed AWMR can get smaller average end-to-end delay by avoiding the shared bottleneck link problem among multiple paths. Using EstiNet, simulation results show that the proposed AWMR outperforms DFS+worst-fit-link in terms of average end-to-end delay, average throughput per flow, and average packet delivery ratio.