PROBLEM TO BE SOLVED: To prevent occurrence of red rust from an end face to be observed in chromium-free coated steel sheet not utilizing chromate treatment or chromate based rust prevention pigments without deteriorating corrosion resistance. SOLUTION: In a chromium-free coated steel sheet, one or more layers of coating films are formed on both surfaces, respectively, of a coating base material comprising a plated steel sheet having a plated layer containing zinc. When one hundred samples of the coated steel sheet cut into a rectangle of 0.5 cm×4.5 cm are immersed in ion exchange water (≤4μS/cm) of 200 ml at 50°C for 30 min under applying ultrasonic vibration with a frequency of 40 kHz, electric conductivity of immersion water is ≥30μS/cm. A coating film of outermost layer contains a compound (preferably an alkali metal phosphate) of 1 to 30% by mass with the proviso that (A) electric conductivity of the water is ≥500μS/cm when the compound is dissolved in ion exchange water (≤4μS/cm) in 0.1% by mass and (B) the compound is not thermally decomposed by 200°C. COPYRIGHT: (C)2009,JPO&INPIT