A diaphragm pump having: a rollingdiaphragm including: - an innercircumferential portion which is supported by a piston that is reciprocally movable in a cylinder, and which elongates along an outer circumferential surface of said piston; - an outer circumferential portion which is supported by said cylinder, and which elongates along an inner circumferential surface of said cylinder; and - a folded portion which is formed by folding back in a tubular space between said cylinder and said piston, to extend from said inner circumferential portion to said outer circumferential portion, said rolling diaphragm being made of a flexible material; and a pump chamber which is separated by said rolling diaphragm in said cylinder, and a volume of which is changed in a manner that the volume is reduced by a projective movement of said piston, and the volume is increased by a retractive movement of said piston, wherein said piston is configured to be reciprocally movable between a maximum projecting position where said piston is mostly projectively moved and a suction position (k) where the retractive movement is performed from the maximum projecting position (f), and between the suction position (k) and an ejection position (t) where the retractive movement is performed from the maximum projecting position (f), and where the projective movement is performed from the suction position (k) characterised in that, said rolling diaphragm is produced in an extended attitude corresponding to an attitude obtained when, by a projective movement of said piston, said outer circumferential portion is eliminated, and a folding of said folded portion is opened, and said rolling diaphragm is set to a state in which, when said piston is at the maximum projecting position (f), the extended attitude is obtained, and when said piston is at the ejection position (t) and on a side of the suction position (k) with respect to the ejection position (t), said rolling diaphragm is maintained in a folded attitude having said folded portion. a rollingdiaphragm including: - an innercircumferential portion which is supported by a piston that is reciprocally movable in a cylinder, and which elongates along an outer circumferential surface of said piston; - an outer circumferential portion which is supported by said cylinder, and which elongates along an inner circumferential surface of said cylinder; and - a folded portion which is formed by folding back in a tubular space between said cylinder and said piston, to extend from said inner circumferential portion to said outer circumferential portion, said rolling diaphragm being made of a flexible material; and - an innercircumferential portion which is supported by a piston that is reciprocally movable in a cylinder, and which elongates along an outer circumferential surface of said piston; - an outer circumferential portion which is supported by said cylinder, and which elongates along an inner circumferential surface of said cylinder; and - a folded portion which is formed by folding back in a tubular space between said cylinder and said piston, to extend from said inner circumferential portion to said outer circumferential portion, said rolling diaphragm being made of a flexible material; and a pump chamber which is separated by said rolling diaphragm in said cylinder, and a volume of which is changed in a manner that the volume is reduced by a projective movement of said piston, and the volume is increased by a retractive movement of said piston, wherein said piston is configured to be reciprocally movable between a maximum projecting position where said piston is mostly projectively moved and a suction position (k) where the retractive movement is performed from the maximum projecting position (f), and between the suction position (k) and an ejection position (t) where the retractive movement is performed from the maximum projecting position (f), and where the projective movement is performed from the suction position (k) characterised in that, said rolling diaphragm is produced in an extended attitude corresponding to an attitude obtained when, by a projective movement of said piston, said outer circumferential portion is eliminated, and a folding of said folded portion is opened, and said rolling diaphragm is set to a state in which, when said piston is at the maximum projecting position (f), the extended attitude is obtained, and when said piston is at the ejection position (t) and on a side of the suction position (k) with respect to the ejection position (t), said rolling diaphragm is maintained in a folded attitude having said folded portion.