An object of the present invention is to provide a tamper-evident structure of syringe that enables a user to recognize at a glance the fact that the syringe is already unsealed. A cap 4 of the syringe 2 includes a cover 5 that covers a distal end of a nozzle 21, a sealing plug 7 that is elastic and seals the distal end of the nozzle 21 in a state of being attached to the inside of the cover 5, and a tamper ring 6 that is cylindrical and is fixed to the syringe 2 with the nozzle 201 inserted into the tamper ring 6. The tamper ring 6 includes a restraining part that is separably connected to the cover 5 in a state where the sealing plug 7 is pressed against the distal end of the nozzle 2 in the axial direction of the tamper ring 6 and thereby elastically compressed within the cover 5.
