We have investigated the quasi-two-dimensional magnetism for the layered transition metal compound (C_nH_2n+1NH₃)₂CuCl₄ (n=10, 14) in the high temperature regions by means of EPR (Electron Paramagnetic Resonance) and SQUID measurements. As a result, the magnetic transitions were reflected in the EPR linewidths and the magnetic suceptibilities in a sensitive manner. Fluctuations of the magnetic susceptibility and a similar variation of the .DELTA. g =(g_{.parallel. -}g_.perp.)g_.parallel. value were also observed around the structural phase transition temperatures.