It has been found that the magnetic susceptibility of synthetic atacamite, Cu2Cl(OH)3, reveals existence of a relaxation phenomenon similar to that in the spin glass. The magnetic susceptibility shows an unusual behavior below 8K; there is a sharp peak in the magnetic susceptibility at about 5.3K when the crystal is cooled in zero magnetic field and the magnetization is a very slow process following a logarithmic law. On the other hand, the susceptibility decreases monotonously as the temperature is raised. The AC magnetic suscpeticibility x' shows a sharp peak at 5.8K, which shifts to higher temperature with increasing AC field frequency.