A negative electrode active material, comprising a secondary particle (210, 230, 250) including a first particle and a second particle wherein each of the first and the second particle is a primary particle, the secondary particle (210, 230, 250) is formed by aggregation of the primary particles, wherein an average particle size D50 of the secondary particle (200, 210, 220, 230, 240, 250) is in a range of 2 to 50 μm, wherein an average particle size D50 is a particle size on the basis of 50% of the particle size distribution of particles as determined by laser diffraction, the first particle includes a first core, and a first surface layer which is disposed on a surface of the first core and contains carbon, and the first core includes: a silicon compound; and a metal compound which includes one or more of a metal oxide and a metal silicate, wherein the metal oxide includes an oxide of one or more metals selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti), the metal silicate includes a silicate of one or more metals selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti) the second particle includes a second core and a second surface layer which is disposed on a surface of the second core and contains carbon, and the second core includes one or more of a silicon and a silicon compound, and the second particle is undoped, characterized in that the silicon compound included in each of the first core and the second core is a silicon oxide (SiO x, 0<x<2) in which silicon is dispersed in a silicon dioxide (SiO 2) matrix, and the metal compound is doped in an amount of 1 to 50 wt% based on the total weight of the first particle. wherein each of the first and the second particle is a primary particle, the secondary particle (210, 230, 250) is formed by aggregation of the primary particles, wherein an average particle size D50 of the secondary particle (200, 210, 220, 230, 240, 250) is in a range of 2 to 50 μm, wherein an average particle size D50 is a particle size on the basis of 50% of the particle size distribution of particles as determined by laser diffraction, the first particle includes a first core, and a first surface layer which is disposed on a surface of the first core and contains carbon, and the first core includes: a silicon compound; and a metal compound which includes one or more of a metal oxide and a metal silicate, wherein the metal oxide includes an oxide of one or more metals selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti), the metal silicate includes a silicate of one or more metals selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti) the second particle includes a second core and a second surface layer which is disposed on a surface of the second core and contains carbon, and the second core includes one or more of a silicon and a silicon compound, and the second particle is undoped, characterized in that the silicon compound included in each of the first core and the second core is a silicon oxide (SiO x, 0<x<2) in which silicon is dispersed in a silicon dioxide (SiO 2) matrix, and the metal compound is doped in an amount of 1 to 50 wt% based on the total weight of the first particle. a silicon compound; and a metal compound which includes one or more of a metal oxide and a metal silicate, wherein the metal oxide includes an oxide of one or more metals selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti), the metal silicate includes a silicate of one or more metals selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti) the second particle includes a second core and a second surface layer which is disposed on a surface of the second core and contains carbon, and the second core includes one or more of a silicon and a silicon compound, and the second particle is undoped, characterized in that the silicon compound included in each of the first core and the second core is a silicon oxide (SiO x, 0<x<2) in which silicon is dispersed in a silicon dioxide (SiO 2) matrix, and the metal compound is doped in an amount of 1 to 50 wt% based on the total weight of the first particle.