Relaxation behavior of ionomer molecule in melt state was investigated by Brownian simulation where motion of a bead-rod chain representing a linear ionomer molecule was calculated in two-dimension. Entanglement between the other molecules was assumed by a repulsive interaction between the chain and randomly located entanglement points. Effect of ion aggregates was also introduced by an attractive interaction between the chain and attractive sites randomly dispersed in the simulation box. Relaxation spectra of end-to-end motion and local bond orientation were obtained in equilibrium calculation for various chain lengths. The effect of the attractive site was discussed on the spectrum. It was found that on the end-to-end motion, the longer the chain was, the more discrepant the spectrum was, while on the bond orientation, the shorter it was, the more discrepant the spectrum was. On the basis of these results, a picture to describe the experimental phenomena was proposed.