Chloroprene-based block copolymer, latex, latex composition, and rubber composition

A chloroprene-based block copolymer, containing 5 to 30% by mass of a polymer block (A) and 70 to 95% by mass of a chloroprene-based polymer block (B), wherein:

• the polymer block (A) is derived from a monomer;
• when the monomer is polymerized alone, a polymer with a glass transition temperature of 80° C. or higher can be obtained;
• the chloroprene-based polymer block (B) includes a chloroprene monomer unit and a polyfunctional monomer unit;
• the polyfunctional monomer is a monomer represented by formula (1) or aromatic polyene monomer;
• in the formula (1), each of R1 and R2 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;
• W1 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;
• Z1 represents any one of oxygen, sulfur, and a structure represented by NR0−;
• R0 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.