Photodissociation spectra of Mg+(H2O)(n) (n=1-5) cluster ions : were examined in the wavelength region from 720 to 250 nm by monitoring the total yield of the fragment ions. The absorption bands exhibit redshifts as large as 17000 cm(-1) with respect to the P-2-S-2 resonance line of the free Mg+ ion and were explained by the shift of this transition as a result of hydration. The spectra also exhibit clear evolution of solvation shell with;the first shell closing at n=3, being consistent with the theoretical prediction. The mass spectra of the fragment ions show the existence of two dissociation processes : the evaporation of water molecules and the photoinduced intracluster reaction to produce the hydrated MgOH+ ion, MgOH+(H2O)(m). The branching fraction between the two processes depends strongly on the solvent number n and also on the photolysis wavelength. The energetics and the dynamics of the dissociation processes were discussed in conjunction with the results of ab initio calculations.