The present invention relates to a gas generator for a restraining device for a vehicle comprising a combustion chamber accommodating a solid gas generating agent therein, an igniter for igniting and burning the solid gas generating agent, the solid gas generating agent having a columnar shape and a through hole in the central portion thereof in the longitudinal direction, an ignition portion of the igniter being disposed to face one end surface of the solid gas generating agent, an outer diameter of the ignition portion being smaller than an outer diameter of the solid gas generating agent and larger than an inner diameter of the through hole.