There is provided a pretensioner. The pretensioner includes: a pipe; a gas generator that generates a gas in the pipe in an emergency case; a gas generator mount on which the gas generator is mounted; a spool driving mechanism that rotates a spool in a direction to retract a seatbelt by the gas generated by the gas generator in the emergency case; a discharge hole formed in the pipe so as to allow communication between inside and outside of the pipe; and a blocking member configured to block the discharge hole from inside of the pipe, the blocking member being configured to open the discharge hole when the blocking member is pressed from outside of the pipe with a pressing force equal to or greater than a given pressing force.