A chloroprene-based block copolymer, contains 5 to 30% by mass of a polymer block and 70 to 95% by mass of a chloroprene-based polymer block, wherein: the polymer block is derived from a monomer; when the monomer is polymerized alone, a polymer with a glass transition temperature of 80°C or higher, determined as described in the description, can be obtained; the chloroprene-based polymer block includes a chloroprene monomer unit and a polyfunctional monomer unit, wherein: the polyfunctional monomer is a monomer represented by formula or aromatic polyene monomer; in the formula, each of R 1 and R 2 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a mercapto group, or a substituted or unsubstituted heterocyclyl group; W 1 represents any one of a saturated or unsaturated hydrocarbon group, a saturated or unsaturated cyclic hydrocarbon group, a saturated or unsaturated hydrocarbon group containing a hetero atom, and a saturated or unsaturated cyclic hydrocarbon group containing a hetero atom; Z 1 represents any one of oxygen, sulfur, and a structure represented by - NR 0 -; R 0 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, mercapto group, or a substituted or unsubstituted heterocyclyl group. the polymer block is derived from a monomer; when the monomer is polymerized alone, a polymer with a glass transition temperature of 80°C or higher, determined as described in the description, can be obtained; the chloroprene-based polymer block includes a chloroprene monomer unit and a polyfunctional monomer unit, wherein: the polyfunctional monomer is a monomer represented by formula or aromatic polyene monomer; in the formula, each of R 1 and R 2 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a mercapto group, or a substituted or unsubstituted heterocyclyl group; W 1 represents any one of a saturated or unsaturated hydrocarbon group, a saturated or unsaturated cyclic hydrocarbon group, a saturated or unsaturated hydrocarbon group containing a hetero atom, and a saturated or unsaturated cyclic hydrocarbon group containing a hetero atom; Z 1 represents any one of oxygen, sulfur, and a structure represented by - NR 0 -; R 0 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, mercapto group, or a substituted or unsubstituted heterocyclyl group. the polyfunctional monomer is a monomer represented by formula or aromatic polyene monomer; in the formula, each of R 1 and R 2 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a mercapto group, or a substituted or unsubstituted heterocyclyl group; W 1 represents any one of a saturated or unsaturated hydrocarbon group, a saturated or unsaturated cyclic hydrocarbon group, a saturated or unsaturated hydrocarbon group containing a hetero atom, and a saturated or unsaturated cyclic hydrocarbon group containing a hetero atom; Z 1 represents any one of oxygen, sulfur, and a structure represented by - NR 0 -; R 0 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, mercapto group, or a substituted or unsubstituted heterocyclyl group.