In vivo 31P NMR spectra were obtained in eight infant brain at 4.7T. Each phosphorus metabolite and its ratio were analyzed to evaluate the brain damage and maturity, and compared with the reported data obtained at the lower field strength, Measurement of T1 relaxation time at 4.7T was done in an infant and a cat brain invivo. PCr/Pi and PCr/$eta$-ATP ratio were used as a marker of brain damage. PME/PDE revealed higher values than those of the reported data obtained at the lower field strength and the defference was partly attributed to the long T1 relaxation time of PME rather than the brain immaturity. Although the resolution of the spectrum was improved at 4.7T, a long repetition time is recommended to minimize T1 difference of phosphorus metabolites of brain at 4.7T.