A gate valve comprising: a valve body (V; VA) configured to be inserted into a fluid pipe through a through-hole formed in the fluid pipe, by movement in an insertion direction that conforms to a diameter direction of the fluid pipe; and a movement mechanism configured to move the valve body (V; VA) in the insertion direction, wherein: the valve body (V; VA) includes a valve main body (20; 20A) and a seal member (30; 30A) that is capable of undergoing elastic deformation and is provided on the valve main body (20; 20A) in a region that covers a holding portion (24; 24A) that protrudes in the insertion direction, the seal member (30; 30A) is configured, when the valve body (V; VA) is moved in the insertion direction by the movement mechanism such that the seal member (30; 30A) comes into contact with an inner wall of the fluid pipe and undergoes elastic deformation, to come into close contact with the inner wall of the fluid pipe and to block a flow of a fluid in the fluid pipe, and a core member (36; 36A) that is separate from the holding portion (24; 24A) and is formed by a harder material than the seal member (30; 30A) is embedded between an outer face (31; 31A) of the seal member (30; 30A) on an insertion direction side and a leading end face (24s; 24sA) on a protruding side of the holding portion (24; 24A), and the core member (36; 36A) is embedded inside the seal member (30; 30A), characterized in that second restriction walls (25; 25A) are formed on the leading end face (24s; 24sA) of the holding portion (24; 24A), the second restriction walls (25; 25A) rising toward the core member (36; 36A) and extending orthogonal to a pipe axis of the fluid pipe at respective end positions of the leading end face (24s; 24sA) in a direction conforming to the pipe axis. a valve body (V; VA) configured to be inserted into a fluid pipe through a through-hole formed in the fluid pipe, by movement in an insertion direction that conforms to a diameter direction of the fluid pipe; and a movement mechanism configured to move the valve body (V; VA) in the insertion direction, wherein: the valve body (V; VA) includes a valve main body (20; 20A) and a seal member (30; 30A) that is capable of undergoing elastic deformation and is provided on the valve main body (20; 20A) in a region that covers a holding portion (24; 24A) that protrudes in the insertion direction, the seal member (30; 30A) is configured, when the valve body (V; VA) is moved in the insertion direction by the movement mechanism such that the seal member (30; 30A) comes into contact with an inner wall of the fluid pipe and undergoes elastic deformation, to come into close contact with the inner wall of the fluid pipe and to block a flow of a fluid in the fluid pipe, and a core member (36; 36A) that is separate from the holding portion (24; 24A) and is formed by a harder material than the seal member (30; 30A) is embedded between an outer face (31; 31A) of the seal member (30; 30A) on an insertion direction side and a leading end face (24s; 24sA) on a protruding side of the holding portion (24; 24A), and the core member (36; 36A) is embedded inside the seal member (30; 30A), characterized in that second restriction walls (25; 25A) are formed on the leading end face (24s; 24sA) of the holding portion (24; 24A), the second restriction walls (25; 25A) rising toward the core member (36; 36A) and extending orthogonal to a pipe axis of the fluid pipe at respective end positions of the leading end face (24s; 24sA) in a direction conforming to the pipe axis. the valve body (V; VA) includes a valve main body (20; 20A) and a seal member (30; 30A) that is capable of undergoing elastic deformation and is provided on the valve main body (20; 20A) in a region that covers a holding portion (24; 24A) that protrudes in the insertion direction, the seal member (30; 30A) is configured, when the valve body (V; VA) is moved in the insertion direction by the movement mechanism such that the seal member (30; 30A) comes into contact with an inner wall of the fluid pipe and undergoes elastic deformation, to come into close contact with the inner wall of the fluid pipe and to block a flow of a fluid in the fluid pipe, and a core member (36; 36A) that is separate from the holding portion (24; 24A) and is formed by a harder material than the seal member (30; 30A) is embedded between an outer face (31; 31A) of the seal member (30; 30A) on an insertion direction side and a leading end face (24s; 24sA) on a protruding side of the holding portion (24; 24A), and the core member (36; 36A) is embedded inside the seal member (30; 30A), characterized in that second restriction walls (25; 25A) are formed on the leading end face (24s; 24sA) of the holding portion (24; 24A), the second restriction walls (25; 25A) rising toward the core member (36; 36A) and extending orthogonal to a pipe axis of the fluid pipe at respective end positions of the leading end face (24s; 24sA) in a direction conforming to the pipe axis.