We loaded nanoparticles of lithium manganese silicate in the mesopores of CMK-1 periodic mesoporous carbon in order to obtain electrode composed of nanoparticles with a good electric conductivity. The structure was analysed by XRD, nitrogen adsorption, and TEM. Two kinds of framework CMK-1 were prepared; CMK-1 (2.0) contains more carbon than CMK-1 (1.0). XRD of these carbons provides two peaks attributed to /41/a structure. The differential curve of discharge profiles of the nanocomposite electrodes LMSx@CMK-1 (1.0) and LMSx@CMK-1 (2.0) has the peaks at 3.2-3.4 V and 4.1 V. These are assigned to the oxidation pairs of Mn2+/Mn3+ and Mn3+/Mn4+, respectively. Assuming that clogging of pores by lithium manganese silicate particles similarly causes the decrease in pore volume both for nitrogen adsorption and Li+ absorption, the net charge-discharge curves for the lithium manganese silicate particles were calculated using those for the composite electrodes and those for the framework carbons without lithium manganese silicate. Then the capacities of lithium manganese silicate nanoparticles are determined to be 240 and 230 mAh/g for LMS0.5@CMK-1 (1.0) and LMS0.5@CMK-1 (2.0), respectively. These results imply that most of the nanoparticles in CMK-1 are susceptible to the electrochemical reaction Li2MnSiO4 = MnSiO4 + 2Li+ + 2e.