Abstract: In a method of continuously annealing steel strip comprising a heating step (A), a soaking step (B), a primary cooling step (C) including a rapid cooling step at least in a second half thereof, an overaging step (D), and a final cooling step (E), inert atmosphere gas containing H.sub.2 gas in the concentration of 30-60% is employed as cooling gas for use in the rapid cooling step, the blowoff temperature of the cooling gas is 30.degree.-150.degree. C., and the blowoff speed of the cooling gas is 100-150 m/sec. The primary cooling method in continuously annealing steel strip provides the primary cooling step (C) including the rapid cooling step which can be carried out with a high efficiency and a low cost.