temperature nearly to 100 u00b0 c the construction of the apparatus in this example is as above described now the function of this apparatus will be stated in the following in the first place a cloth to be bleached 1 is immersed in a bleaching solution comprising a slightly alkaline sodium chlorite solution with a concentration of about 0 5 1 0 in the bleaching solution tank 2 at the ordinary temperature the cloth soaked with the sodium chlorite solution is squeezed by means of the squeeze roll 3 appropriately and the thus squeezed cloth is transferred into the wet heat treating chamber 4 which has been heated to a temperature nearly 100 u00b0 c previously by using the heating means 7 in the wet heat treating chamber 4 a volatile activation agent for instance acetic acid is supplied in the state of mists by using the means 5 so as to make the atmosphere in the chamber acidic with a ph of 3 4 instead of acetic acid such activation agent as an inorganic acid and a carbonyl compound as already mentioned may also be used the cloth is transported continuously therethrough zigzag forming snaky undulations with no tension by means of the guide rolls 6 at a temperature in the range of 90 u00b0 95 u00b0 c and thus the continuous bleaching of a long cloth in object is done in a short time of within 2 minutes the cloth is bleached uniformly and excellently and particularly with no formation of creases of which formation can by no means be.