A golf ball (2, 102) consists of a spherical core (4, 104) and a cover (6, 106) covering the core (4, 104) and including two or more layers, wherein when distances (%) from a central point of the core (4, 104) to nine points and JIS-C hardnesses at the nine points, which nine points are obtained by dividing a region from the central point of the core (4, 104) to a surface of the core (4, 104) at intervals of 12.5% of a radius of the core (4, 104), are plotted in a graph, R 2 of a linear approximation curve obtained by a least-square method is equal to or greater than 0.95, wherein R 2 is calculated by squaring a correlation coefficient R, wherein the correlation coefficient R is calculated by dividing the covariance of the distance (%) from the central point and the hardness (JIS-C) by the standard deviation of the distance (%) from the central point and the standard deviation of the hardness (JIS-C), the JIS-C hardness Hi of the innermost layer of the cover (6, 106) is greater than the JIS-C hardness Hs at the surface of the core (4, 104) or the JIS-C hardness Hi of the innermost layer of the cover (6, 104) is equal to or less than the JIS-C hardness Hs at the surface of the core (4, 104), and the core (4, 104) is formed by a rubber composition being crosslinked, wherein the rubber composition includes: (a) a base rubber, (b) a co-crosslinking agent, wherein the co-crosslinking agent (b) is: an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; or a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (c) a crosslinking initiator, characterized in that the rubber composition further includes: a carboxylic acid and/or a salt thereof, wherein the carboxylic acid and/or salt thereof is different from the co-crosslinking agent (b). when distances (%) from a central point of the core (4, 104) to nine points and JIS-C hardnesses at the nine points, which nine points are obtained by dividing a region from the central point of the core (4, 104) to a surface of the core (4, 104) at intervals of 12.5% of a radius of the core (4, 104), are plotted in a graph, R 2 of a linear approximation curve obtained by a least-square method is equal to or greater than 0.95, wherein R 2 is calculated by squaring a correlation coefficient R, wherein the correlation coefficient R is calculated by dividing the covariance of the distance (%) from the central point and the hardness (JIS-C) by the standard deviation of the distance (%) from the central point and the standard deviation of the hardness (JIS-C), the JIS-C hardness Hi of the innermost layer of the cover (6, 106) is greater than the JIS-C hardness Hs at the surface of the core (4, 104) or the JIS-C hardness Hi of the innermost layer of the cover (6, 104) is equal to or less than the JIS-C hardness Hs at the surface of the core (4, 104), and the core (4, 104) is formed by a rubber composition being crosslinked, wherein the rubber composition includes: (a) a base rubber, (b) a co-crosslinking agent, wherein the co-crosslinking agent (b) is: an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; or a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (c) a crosslinking initiator, characterized in that the rubber composition further includes: a carboxylic acid and/or a salt thereof, wherein the carboxylic acid and/or salt thereof is different from the co-crosslinking agent (b). (a) a base rubber, (b) a co-crosslinking agent, wherein the co-crosslinking agent (b) is: an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; or a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; or a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (c) a crosslinking initiator, characterized in that the rubber composition further includes: a carboxylic acid and/or a salt thereof, wherein the carboxylic acid and/or salt thereof is different from the co-crosslinking agent (b). a carboxylic acid and/or a salt thereof, wherein the carboxylic acid and/or salt thereof is different from the co-crosslinking agent (b).