© 2018-2019 by JSME We experimentally investigated the flow mixing characteristics in a cross-flow plane in a bed of randomly packed spheres with a bed-to-bead ratio of 6.3. The velocity fields on four transverse planes were obtained by applying the matched-index-of-refraction (MIR) and time-resolved particle image velocimetry (TR-PIV) techniques at Reynolds numbers of 700 and 1,200. The combination of the MIR and TR-PIV techniques allow the flow to be analyzed non-invasively. From the obtained TR-PIV velocity vector fields, the first- and second-order flow statistics, such as mean velocity, root-mean-square fluctuating velocity, and Reynolds stress, were computed and presented in the paper. The TR-PIV results revealed various flow patterns in the transverse plane of the facility of randomly packed spheres, such as swirling flow structures, by-pass flows, and circulation flow regions.