Provided are: a steel sheet having a high strength and excellent stretch formability; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which the integration degree of the (111) orientation of ferrite is 3.0 or higher, and the integration degree of the (252) orientation of martensite and tempered martensite is 5.0 or lower. The method of producing the steel sheet includes: the step of continuously casting a molten steel having the prescribed chemical composition, and performing 5 to 40% rolling reduction at a temperature of 800° C. to lower than 1,200° C. in a period after the continuous casting until cooling to room temperature; the hot rolling step of performing hot rolling with a finishing temperature of 650 to 950° C.; the step of coiling the resulting hot-rolled steel sheet at a coiling temperature of 400 to 700° C.; the step of retaining the hot-rolled steel sheet at (coiling start temperature+20° C. to 100° C.) for 5 to 300 minutes; the step of cold rolling the hot-rolled steel sheet at a rolling reduction ratio of 10.0 to 90.0%; and the step of annealing the resulting cold-rolled steel sheet at 700 to 900° C.