A linear friction welding apparatus for welding a first member and a second member (Di) together by friction welding by pressing the first member and the second member (Di) against each other while causing a relative oscillation movement between the first member and the second member (Di), the apparatus comprising: a pressure mechanism configured to press the first member and the second member (Di) against each other; a first holding member configured to hold the first member; and a second holding member configured to hold the second member (Di) and caused to advance and retreat in a direction conforming to a pressure axis, the pressure mechanism comprising: a pressure force application member caused to advance and retreat in the direction conforming to the pressure axis; and a load sensor attached to the second holding member and configured to measure a pressure force in the direction conforming to the pressure axis, characterized in that the pressure mechanism comprises a support mechanism fixed to the second holding member, connected to the pressure force application member, and configured to support a moment load applied from the pressure force application member, the support mechanism comprising: a base member fixed to the second holding member; and a support member including a pressure force transmission portion located between the load sensor and the pressure force application member, engaged with the base member so as to advance and retreat in the direction conforming to the pressure axis, and connected to a tip of the pressure force application member. a pressure mechanism configured to press the first member and the second member (Di) against each other; a first holding member configured to hold the first member; and a second holding member configured to hold the second member (Di) and caused to advance and retreat in a direction conforming to a pressure axis, the pressure mechanism comprising: a pressure force application member caused to advance and retreat in the direction conforming to the pressure axis; and a load sensor attached to the second holding member and configured to measure a pressure force in the direction conforming to the pressure axis, a pressure force application member caused to advance and retreat in the direction conforming to the pressure axis; and a load sensor attached to the second holding member and configured to measure a pressure force in the direction conforming to the pressure axis, characterized in that the pressure mechanism comprises a support mechanism fixed to the second holding member, connected to the pressure force application member, and configured to support a moment load applied from the pressure force application member, the support mechanism comprising: a base member fixed to the second holding member; and a support member including a pressure force transmission portion located between the load sensor and the pressure force application member, engaged with the base member so as to advance and retreat in the direction conforming to the pressure axis, and connected to a tip of the pressure force application member. the pressure mechanism comprises a support mechanism fixed to the second holding member, connected to the pressure force application member, and configured to support a moment load applied from the pressure force application member, the support mechanism comprising: a base member fixed to the second holding member; and a support member including a pressure force transmission portion located between the load sensor and the pressure force application member, engaged with the base member so as to advance and retreat in the direction conforming to the pressure axis, and connected to a tip of the pressure force application member. a base member fixed to the second holding member; and a support member including a pressure force transmission portion located between the load sensor and the pressure force application member, engaged with the base member so as to advance and retreat in the direction conforming to the pressure axis, and connected to a tip of the pressure force application member.