This paper applies non-orthogonal multiple access (NOMA) with joint detection to a heterogeneous network (HetNet). The HetNet is a system in which pico base stations are placed in a macrocell and shares frequency resources with a macro base station. In the HetNet, the offloading of traffic to the pico base stations is limited since the transmission power of the macro base station is large. To achieve better spectrum efficiency with offloading, NOMA HetNet is proposed. In the proposed scheme, the desired signal is extracted with joint detection to realize offloading to a pico base station. Numerical results obtained through system level simulation show that NOMA doubles the total throughput by enhancing traffic offloading.