Organic magnetic materials were fabricated by the arc discharge method with starting materials of nitrogen gas and triethylamine. After nitrogen gas or gaseous triethylamine was introduced into the chamber, an arc was discharged between carbon electrodes with a purity of 99.99%. The as-made samples were annealed in decreased air from 400°C to 1000°C for 3 hours. The carbonaceous sample prepared in nitrogen gas was a diamagnetic material, while the sample made from triethylamine was a ferromagnetic-like material whose magnetization was around 0.02 emu/g at room temperature. After annealing between 500°C and 600°C, the magnetization of the ferromagnetic-like material increased by around 3 times as much as that of as-made one. However, the spin density, measured by electron spin resonance, decreased with increasing annealing temperature; in particular, it fell rapidly between 500°C and 600°C. Therefore, the linewidth of the ferromagnetic-like carbonaceous material after annealing at 500°C and 600°C was narrower than that of the as-made material, and the intensified spin interaction suggested an increase in the magnetization.