A production method for a modified conjugated diene-based polymer, comprising: a polymerizing step of obtaining a conjugated diene-based polymer having an active end by polymerizing or copolymerizing a conjugated diene compound or a conjugated diene compound and an aromatic vinyl compound with an alkali metal compound or an alkaline earth metal compound used as a polymerization initiator; a branching step of introducing a branch structure by reacting a styrene derivative with the active end of the conjugated diene-based polymer; and a modifying step of reacting the active end of the conjugated diene-based polymer formed after the branching step with a compound having a total of two or more groups of a group "-C(R 1)=N-A 1 " and/or a group "-N=C(R 1)-A 1 ", wherein R 1 represents a hydrogen atom or a hydrocarbyl group, and A 1 represents a monovalent group having an alkoxysilyl group, wherein the styrene derivative is a compound represented by the following formula and/or the following formula: wherein Q 1 represents any one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and may have a branch structure in a part thereof; X 1, X 2 and X 3 represent a single bond, or an organic group containing any one selected from the group consisting of carbon, hydrogen, nitrogen, sulfur, and oxygen; and Y 1, Y 2, and Y 3 represent any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom, are respectively independent, and may be the same or different. a polymerizing step of obtaining a conjugated diene-based polymer having an active end by polymerizing or copolymerizing a conjugated diene compound or a conjugated diene compound and an aromatic vinyl compound with an alkali metal compound or an alkaline earth metal compound used as a polymerization initiator; a branching step of introducing a branch structure by reacting a styrene derivative with the active end of the conjugated diene-based polymer; and a modifying step of reacting the active end of the conjugated diene-based polymer formed after the branching step with a compound having a total of two or more groups of a group "-C(R 1)=N-A 1 " and/or a group "-N=C(R 1)-A 1 ", wherein R 1 represents a hydrogen atom or a hydrocarbyl group, and A 1 represents a monovalent group having an alkoxysilyl group, wherein the styrene derivative is a compound represented by the following formula and/or the following formula: wherein Q 1 represents any one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and may have a branch structure in a part thereof; X 1, X 2 and X 3 represent a single bond, or an organic group containing any one selected from the group consisting of carbon, hydrogen, nitrogen, sulfur, and oxygen; and Y 1, Y 2, and Y 3 represent any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom, are respectively independent, and may be the same or different. wherein Q 1 represents any one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and may have a branch structure in a part thereof; X 1, X 2 and X 3 represent a single bond, or an organic group containing any one selected from the group consisting of carbon, hydrogen, nitrogen, sulfur, and oxygen; and Y 1, Y 2, and Y 3 represent any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom, are respectively independent, and may be the same or different.