Intel oneAPI is a programming framework that accepts various accelerators such as GPUs, FPGAs, and multi-core CPUs, with a focus on HPC applications. Users can apply their code written in a single language, DPC++, to this heterogeneous programming environment. However, in practice, it is not easy to apply to different accelerators, especially for non-Intel devices such as NVIDIA and AMD GPUs. We have successfully constructed a oneAPI environment set to utilize the single DPC++ programming to handle true multi-hetero acceleration including NVIDIA GPU and Intel FPGA simultaneously. In this paper, we will show how this is done and what kind of applications can be targeted.