An ink jet printing ink for use in an ink jet printing method. The ink is ejected from a print head by the action of thermal energy and includes water, a self-dispersing pigment, and at least two types of resin particles. One of the at least two types of resin particles (resin particle A) and another of the at least two types of resin particles (resin particle B) have an average particle size of 80 nm or more but 220 nm or less and an acid value of 25 mgKOH/g or more but 150 mgKOH/g or less. The resin particle A has a glass transition temperature of 25 degrees Celsius or less. The resin particle B has a glass transition temperature of 25 degrees Celsius or more. A difference in glass transition temperature between the resin particle A and the resin particle B is 10 degrees Celsius or more.