A surface-coated boron nitride sintered body tool, in which at least a cutting edge portion includes a cubic boron nitride sintered body and a coating film formed on a surface of the cubic boron nitride sintered body, said cubic boron nitride sintered body comprising 30 vol% or more and 80 vol% or less of cubic boron nitride particles, and further comprising a binder phase including at least one compound selected from the group consisting of nitride, carbide, boride, oxide, and solid solutions thereof in group 4 elements, group 5 elements and group 6 elements in a periodic table, an aluminum compound, and inevitable impurities, said coating film including an A layer and a B layer, said A layer being formed of columnar crystals and including MLa za1, wherein M represents one or more of group 4 elements, group 5 elements and group 6 elements in the periodic table, Al and Si; La represents one or more of B, C, N, and O; and za1 is 0.85 or more and 1.0 or less, said B layer being formed of columnar crystals and formed by alternately stacking one or more of each of two or more compound layers having different compositions, said compound layers each having a thickness of 0.5 nm or more and 300 nm or less, one of said compound layers being a B1 compound layer, said B1 compound layer including (Ti 1-xb1-yb1 Si xb1 M1 yb1) (C 1-zb1 N zb1), wherein M1 represents one or more of group 4 elements except for Ti, group 5 elements and group 6 elements in the periodic table, and Al; xb1 is 0.01 or more and 0.25 or less; yb1 is 0 or more and 0.7 or less; and zb1 is 0.4 or more and 1 or less, one of said compound layers being a B2 compound layer, said B2 compound layer being different from said B1 compound layer, and including (Al 1-xb2 M2 xb2) (C 1-zb2 N zb2), wherein M2 represents one or more of group 4 elements, group 5 elements and group 6 elements in the periodic table, and Si; xb2 is 0.2 or more and 0.7 or less; and zb2 is 0.4 or more and 1 or less, said A layer having a thickness of 0.2 μm or more and 10 μm or less, said B layer having a thickness of 0.05 μm or more and 5 μm or less, and said coating film having an entire thickness of 0.3 μm or more and 15 μm or less, a particle size Wa of each of said columnar crystals included in said A layer being 10 nm or more and 400 nm or less, and a particle size Wb of each of said columnar crystals included in said B layer being 5 nm or more and 70 nm or less, said particle size Wa being the average width of said columnar crystals included in said A layer, said particle size Wb being the average width of said columnar crystals included in said B layer, and said particle size Wa and said particle size Wb satisfy a relation of 1 < Wa/Wb ≤ 30. said cubic boron nitride sintered body comprising 30 vol% or more and 80 vol% or less of cubic boron nitride particles, and further comprising a binder phase including at least one compound selected from the group consisting of nitride, carbide, boride, oxide, and solid solutions thereof in group 4 elements, group 5 elements and group 6 elements in a periodic table, an aluminum compound, and inevitable impurities, said coating film including an A layer and a B layer, said A layer being formed of columnar crystals and including MLa za1, wherein M represents one or more of group 4 elements, group 5 elements and group 6 elements in the periodic table, Al and Si; La represents one or more of B, C, N, and O; and za1 is 0.85 or more and 1.0 or less, said B layer being formed of columnar crystals and formed by alternately stacking one or more of each of two or more compound layers having different compositions, said compound layers each having a thickness of 0.5 nm or more and 300 nm or less, one of said compound layers being a B1 compound layer, said B1 compound layer including (Ti 1-xb1-yb1 Si xb1 M1 yb1) (C 1-zb1 N zb1), wherein M1 represents one or more of group 4 elements except for Ti, group 5 elements and group 6 elements in the periodic table, and Al; xb1 is 0.01 or more and 0.25 or less; yb1 is 0 or more and 0.7 or less; and zb1 is 0.4 or more and 1 or less, one of said compound layers being a B2 compound layer, said B2 compound layer being different from said B1 compound layer, and including (Al 1-xb2 M2 xb2) (C 1-zb2 N zb2), wherein M2 represents one or more of group 4 elements, group 5 elements and group 6 elements in the periodic table, and Si; xb2 is 0.2 or more and 0.7 or less; and zb2 is 0.4 or more and 1 or less, said A layer having a thickness of 0.2 μm or more and 10 μm or less, said B layer having a thickness of 0.05 μm or more and 5 μm or less, and said coating film having an entire thickness of 0.3 μm or more and 15 μm or less, a particle size Wa of each of said columnar crystals included in said A layer being 10 nm or more and 400 nm or less, and a particle size Wb of each of said columnar crystals included in said B layer being 5 nm or more and 70 nm or less, said particle size Wa being the average width of said columnar crystals included in said A layer, said particle size Wb being the average width of said columnar crystals included in said B layer, and said particle size Wa and said particle size Wb satisfy a relation of 1 < Wa/Wb ≤ 30.