The present invention prevents oozing of an electrolyte solution from an electrode. An electrode for lithium ion secondary batteries, which comprises an electrode active material and a semisolid electrolyte, and wherein: the semisolid electrolyte comprises an organic solvent or an ionic liquid and a lithium salt; the electrode for lithium ion secondary batteries comprises nanofibers; the nanofibers are composed of a cellulose resin or a polyacrylate resin; the wire diameters of the nanofibers are from 0.01 mu m to 1 mu m (inclusive); and the average of the pore diameters of an electrode mixture layer, which is obtained by removing the ionic liquid and the lithium salt from the electrode for lithium ion secondary batteries, as determined by means of a mercury porosimeter is from 0.001 mu mto 0.5 mu m (inclusive).