A capsule having a liquid enclosed therein, the capsule comprising: a capsule body formed to be elastically deformable in a cylindrical shape, the capsule body having an end wall that closes a distal end thereof, and an open end that opens a proximal end thereof, the capsule body accommodating the liquid thereinside; and a blocking wall provided at the open end of the capsule body, the blocking wall closing the open end so as to contain the liquid inside the capsule body, wherein the end wall includes: a central portion; an outer peripheral portion in an annular shape, the outer peripheral portion surrounding the central portion, the outer peripheral portion projecting more frontward of the distal end of the capsule body than the central portion so as to form the end wall as a recessed wall; and a thin-walled region provided at the central portion, the thin-walled region having a thinner thickness than thicknesses of the end wall and a peripheral wall of the capsule body, wherein the thin-walled portion is breakable to inject the liquid from the capsule wherein the outer peripheral portion of the end wall is elastically deformable in an elliptical shape by an external force applied to a peripheral wall of the capsule body, wherein the thin-walled region has multiple grooves radially arranged at the central portion or is formed as a circular shape at the central portion, and wherein in case that the thin-walled region has the circular shape, the central portion is formed as a hemispheric portion that is recessed inward of the capsule body to be in a hemispheric shape, and the thickness of the central portion is gradually increased from the thin-walled region toward the outer peripheral region. a capsule body formed to be elastically deformable in a cylindrical shape, the capsule body having an end wall that closes a distal end thereof, and an open end that opens a proximal end thereof, the capsule body accommodating the liquid thereinside; and a blocking wall provided at the open end of the capsule body, the blocking wall closing the open end so as to contain the liquid inside the capsule body, a central portion; an outer peripheral portion in an annular shape, the outer peripheral portion surrounding the central portion, the outer peripheral portion projecting more frontward of the distal end of the capsule body than the central portion so as to form the end wall as a recessed wall; and a thin-walled region provided at the central portion, the thin-walled region having a thinner thickness than thicknesses of the end wall and a peripheral wall of the capsule body, wherein the thin-walled portion is breakable to inject the liquid from the capsule wherein the outer peripheral portion of the end wall is elastically deformable in an elliptical shape by an external force applied to a peripheral wall of the capsule body, wherein the thin-walled region has multiple grooves radially arranged at the central portion or is formed as a circular shape at the central portion, and wherein in case that the thin-walled region has the circular shape, the central portion is formed as a hemispheric portion that is recessed inward of the capsule body to be in a hemispheric shape, and the thickness of the central portion is gradually increased from the thin-walled region toward the outer peripheral region.