The electrochemical activation process of the so-called "alkali-treated soft carbon" (ASC) has been examined in organic electrolyte solutions. SEM observation demonstrated that the edge plane of graphene structure of the ASC particle becomes rough after the activation, and XRD measurements indicated that the average lattice constant of graphene stacking in ASC increases after the activation process. Ex-situ Li-7 NMR measurements proved that the insertion of cation (Li+) into the pore structure of ASC is associated with the activation process in the electrolyte dissolving Li salt. The pore-size distribution determined from N-2-gas adsorption for ASC electrodes before and after the electrochemical activation indicates that the pore structure becomes developed after the electrochemical polarization, especially in the pore-diameter range of 2-10 nm. A schematic model of the activation process has been presented, which includes electrochemical insertion of ions into the inside of the ASC.