A syringe comprising: a syringe outer tube; and a gasket which is connected to a pusher having a male screw formed on an outer peripheral portion of a distal end thereof, by screw engagement with the male screw of the pusher, the gasket being slid within a syringe outer tube by operation of the pusher in longitudinal directions thereof, the gasket is made of an elastic material, the gasket comprising: a gasket body having a hollow section and a female screw formed on an inner peripheral portion of the hollow section, the female screw being screw-engaged with the male screw; and at least a first projection and a second projection which are projectingly formed on an outer peripheral portion of the gasket body so as to extend in a circumferential direction of the outer peripheral portion and which are arranged so as to be spaced from each other along an axial direction of the gasket body, the at least first and second projections (31, 32) making firm contact with an inner peripheral surface of the syringe outer tube, whereby liquid tightness is maintained, wherein a screw thread of the female screw has an intersection part at which a foot portion of at least the second projection and a foot portion of the screw thread of the female screw overlap with each other, characterized in that in an uninserted state in which the gasket is not yet inserted into the syringe outer tube, the screw thread having the intersection part has a height smaller than a height of a screw thread located at a portion other than the screw thread having the intersection part in the female screw. a syringe outer tube; and a gasket which is connected to a pusher having a male screw formed on an outer peripheral portion of a distal end thereof, by screw engagement with the male screw of the pusher, the gasket being slid within a syringe outer tube by operation of the pusher in longitudinal directions thereof, the gasket is made of an elastic material, the gasket comprising: a gasket body having a hollow section and a female screw formed on an inner peripheral portion of the hollow section, the female screw being screw-engaged with the male screw; and at least a first projection and a second projection which are projectingly formed on an outer peripheral portion of the gasket body so as to extend in a circumferential direction of the outer peripheral portion and which are arranged so as to be spaced from each other along an axial direction of the gasket body, the at least first and second projections (31, 32) making firm contact with an inner peripheral surface of the syringe outer tube, whereby liquid tightness is maintained, wherein a screw thread of the female screw has an intersection part at which a foot portion of at least the second projection and a foot portion of the screw thread of the female screw overlap with each other, characterized in that in an uninserted state in which the gasket is not yet inserted into the syringe outer tube, the screw thread having the intersection part has a height smaller than a height of a screw thread located at a portion other than the screw thread having the intersection part in the female screw. a gasket body having a hollow section and a female screw formed on an inner peripheral portion of the hollow section, the female screw being screw-engaged with the male screw; and at least a first projection and a second projection which are projectingly formed on an outer peripheral portion of the gasket body so as to extend in a circumferential direction of the outer peripheral portion and which are arranged so as to be spaced from each other along an axial direction of the gasket body, the at least first and second projections (31, 32) making firm contact with an inner peripheral surface of the syringe outer tube, whereby liquid tightness is maintained, wherein a screw thread of the female screw has an intersection part at which a foot portion of at least the second projection and a foot portion of the screw thread of the female screw overlap with each other, characterized in that in an uninserted state in which the gasket is not yet inserted into the syringe outer tube, the screw thread having the intersection part has a height smaller than a height of a screw thread located at a portion other than the screw thread having the intersection part in the female screw.