The flatwork ironer comprises a heating cylinder (1), a plurality of conveying bands (2), defining said conveying bands (2) a plurality of zones in an introduction area of articles to be ironed, and a plurality of temperature sensors (3) of said heating cylinder (1), indication means for indicating at least one zone (5) of the conveying bands where the articles to be ironed must be placed according to the temperature detected by said plurality of sensors (3), wherein said indicating means are placed in said are for introducing the articles to be ironed.It permits to place correctly the articles to be ironed in the correct position not looking away from the introduction area.