Abstract Recent developments of the high-field facility in Kobe University are presented. A far infrared radiation (FIR) laser system, which can generate electromagnetic waves from 500 GHz to 3 THz has been installed. Now the frequency region for high-field ESR is extended from 30 GHz to 3 THz using Gunn oscillators, BWOs and a FIR laser. Recent high-field ESR results of quantum spin systems CsFeBr3 and Cu3(CO3)2(OH)2 using these light sources are presented. CsFeBr3 is known as a field-induced antiferromagnetic ordering substance, and we found new ESR modes in the high-field phase of CsFeBr3 for B//c at 2.0 K . Cu3(CO3)2(OH)2 is the model substance for the S= 1 2 quantum diamond chain, and we observed the direct transition in the ESR measurement at 1.9 K for B//c.