A modified particle obtained by a process containing contacting a Bi compound, a compound having an electron-withdrawing group and an active hydrogen and particle; and a catalyst component for addition polymerization containing the modified particle; a catalyst for addition polymerization prepared by a process containing contacting the modified particle (A) and a transition metal compound of Groups 3 to 11 or lantanide series (B); and a catalyst for addition polymerization prepared by a process containing contacting the modified particle (A) and a transition metal compound of Groups 3 to 11 or lantanide series (B) and an orbanoaluminum compound (C); and a process for producing an addition polymer with the catalyst.