An inhalation device suitable for delivery of the medicament in dry powder form from a blister package composed of a plurality of blister pockets which are spaced at equal intervals, each of which comprises medicament in dry powder form; the inhalation device comprising: - a mouthpiece enabling the patient to inhale the medicament in dry powder form from the opened blister in use; - a gear mechanism enabling in use the blister package to be indexed and the medicament in dry powder form to become ready for inhalation; - a rotatable mouthpiece cover hiding the mouthpiece and triggering the gear mechanism; - a drive gear which is a component of the gear mechanism and is joined with the mouthpiece cover via a connection point of a mouthpiece cover, and - a housing situated between an upper housing member and a lower housing member in which the blister package and the gear mechanism are enclosed, and - a stopper for preventing the movement of the mouthpiece cover characterized in that: the stopper consists of a pawl, a pressing button and a supporting part; wherein the pawl is engaged with a recess part on the inside surface of the mouthpiece cover to prevent the movement of the mouthpiece cover when the mouthpiece cover is in a position in which the mouthpiece is completely covered, and the pressing button that moves synchronously with the pawl is pressed to enable the mouthpiece cover to be rotated for the actuation of the inhalation device as the supporting part is sprung to allow the pressing button to be pressed. - a mouthpiece enabling the patient to inhale the medicament in dry powder form from the opened blister in use; - a gear mechanism enabling in use the blister package to be indexed and the medicament in dry powder form to become ready for inhalation; - a rotatable mouthpiece cover hiding the mouthpiece and triggering the gear mechanism; - a drive gear which is a component of the gear mechanism and is joined with the mouthpiece cover via a connection point of a mouthpiece cover, and - a housing situated between an upper housing member and a lower housing member in which the blister package and the gear mechanism are enclosed, and - a stopper for preventing the movement of the mouthpiece cover characterized in that: the stopper consists of a pawl, a pressing button and a supporting part; wherein the pawl is engaged with a recess part on the inside surface of the mouthpiece cover to prevent the movement of the mouthpiece cover when the mouthpiece cover is in a position in which the mouthpiece is completely covered, and the pressing button that moves synchronously with the pawl is pressed to enable the mouthpiece cover to be rotated for the actuation of the inhalation device as the supporting part is sprung to allow the pressing button to be pressed. the stopper consists of a pawl, a pressing button and a supporting part; wherein the pawl is engaged with a recess part on the inside surface of the mouthpiece cover to prevent the movement of the mouthpiece cover when the mouthpiece cover is in a position in which the mouthpiece is completely covered, and the pressing button that moves synchronously with the pawl is pressed to enable the mouthpiece cover to be rotated for the actuation of the inhalation device as the supporting part is sprung to allow the pressing button to be pressed.