In this study, the mixing of temperature-stratified liquid metal free-surface flow by a delta-wing obstacle installed on the channel bottom has been experimentally and numerically investigated in the presence of a transverse magnetic field. The surface temperature distribution of the channel was measured by using 25 thermocouples (TCs) embedded in the channel bottom, downstream of the obstacle, which was located upstream of the heater installed at the free-surface. The experiments were conducted for the turbulent flow region where Re = 12,000 and in the range of N = 0–5.02 in the presence of the transverse magnetic field. As for the laminar flow region, it is difficult to carry out the experiment, so the numerical simulations were conducted using Re = 2,300 and in the range of N = 0–10. According to the comparison of numerical results with and without the delta-wing obstacle in laminar flow region, the entire temperature distribution with the obstacle was warmer than that without the obstacle. This was consistent with the expectation that a delta-wing obstacle would increase thermal mixing.