Magnetic properties of organic radical crystal, 3-(4-chlorophenyl)-1,5-dimethyl-6-thioxoverdazyl (p-CDTV), have been studied by measuring heat capacity and ac susceptibility above 0.13 K in external magnetic fields of 0-30 kOe. The p-CDTV has been found to be a new and bulk ferromagnet with the second highest Curie temperature T-c=0.68 +/- 0.02 K of genuine organic ferromagnet. The p-CDTV behaves as a quasi-one-dimensional Heisenberg ferromagnet with the intrachain exchange interaction of 2J/k(B)=+12.0 +/- 0.6 K above the transition temperature T,. The interchain exchange interaction zJ’/k(B) was estimated to be +0.21 +/- 0.02 K, where z is the number of interchain bonds per spin.