To realize a mixer, with which super quick setting concrete can be efficiently and uniformly agitated in a short time and quickly discharged and, in addition, which is smoothly operable/kneadable with neither clogging nor adhesion-solidification of a kneaded matter, and an agitating method.

In order to realize the smooth discharge of the cement in a bag and the speeding-up of the discharging/feeding of cement, the cement is dropped in a kneading tank at the lower side of a protective net by unsealing a cement bag under the condition that outside air enters in the cement bag by being broken with a cutting blade by putting the cement bag on the top side of the cutting blade provided onto the protective net under the condition that the barrel large-meshed protective net is covered on the kneading tank built in with an agitating unit formed by fixing agitating rods to a horizontal rotating shaft radially and axially with spaces. In addition, this mixer has a structure, in which a smooth and quick kneading processing is possible by suppressing an evil such as the bonding of the kneaded matter to the periphery of the kneading tank to the minimum during the period ranging from the start to the end of kneading of the quick setting concrete and discharging.