A magnetic field of up to 12 T was applied during the sintering process of pure MgB2 and carbon nanotube (CNT) doped MgB2 wires. The authors have demonstrated that magnetic field processing results in grain refinement, homogeneity, and enhancement in Jc(H) and Hirr. The extent of improvement in Jc increases with increasing field. The Jc for a 10 T field processed CNT doped sample increases by a factor of 3 at 10 K and 8 T and at 20 K and 5 T, respectively. Hirr for the 10 T field processed CNT doped sample reached 9 T at 20 K, which exceeded the best value of SiC doped MgB2 at 20 K. Magnetic field processing reduces the resistivity in CNT doped MgB2, straightens the entangled CNTs, and improves the adherence between CNTs and the MgB2 matrix.