Apush-up device, comprising: a tube shaped case that is adapted to be fixed at a side of a second member that faces a first member; a rod that is retained inside the case so as to be capable of sliding, and that juts out from inside the case to adopt an advanced position pushing out the first member; a rod biasing member that is positioned between the case and the rod, and that is compressed under elastic deformation inside the case, so as to bias the rod in a jutting out direction pushing the rod out from inside the case; a lock mechanism including: a slide cam that moves together with the rod in the jutting out direction, a rotation cam that is provided at a rear side of the slide cam in the jutting out direction and that is capable of relative rotation with respect to the slide cam about an axis of the rod, an engagement projection that juts out from one of an outer peripheral face of the rotation cam or the inner peripheral face of the case, a lock groove that is positioned at another of the outer peripheral face of the rotation cam or the inner peripheral face of the case, that includes a lock portion into which the engagement projection fits, the engagement projection that has been fitted into the lock portion being disengageable from the lock portion by the rotation cam rotating due to the rotation cam disengaging from the slide cam, and with the lock mechanism positioned between the case and the rod, and locking the rod in a retracted position in the case due to the rotation cam engaging with the slide cam and fitting the engagement projection into the lock portion and rotating due to the rod being pressed in against a biasing force of the rod biasing member; characterized in that: a rotation cam biasing member is provided at a rear side of the rotation cam in the jutting out direction inside the case and separately from the rod biasing member, and that biases the rotation cam toward the jutting out direction. a tube shaped case that is adapted to be fixed at a side of a second member that faces a first member; a rod that is retained inside the case so as to be capable of sliding, and that juts out from inside the case to adopt an advanced position pushing out the first member; a rod biasing member that is positioned between the case and the rod, and that is compressed under elastic deformation inside the case, so as to bias the rod in a jutting out direction pushing the rod out from inside the case; a lock mechanism including: a slide cam that moves together with the rod in the jutting out direction, a rotation cam that is provided at a rear side of the slide cam in the jutting out direction and that is capable of relative rotation with respect to the slide cam about an axis of the rod, a slide cam that moves together with the rod in the jutting out direction, a rotation cam that is provided at a rear side of the slide cam in the jutting out direction and that is capable of relative rotation with respect to the slide cam about an axis of the rod, an engagement projection that juts out from one of an outer peripheral face of the rotation cam or the inner peripheral face of the case, a lock groove that is positioned at another of the outer peripheral face of the rotation cam or the inner peripheral face of the case, that includes a lock portion into which the engagement projection fits, the engagement projection that has been fitted into the lock portion being disengageable from the lock portion by the rotation cam rotating due to the rotation cam disengaging from the slide cam, and with the lock mechanism positioned between the case and the rod, and locking the rod in a retracted position in the case due to the rotation cam engaging with the slide cam and fitting the engagement projection into the lock portion and rotating due to the rod being pressed in against a biasing force of the rod biasing member; characterized in that: a rotation cam biasing member is provided at a rear side of the rotation cam in the jutting out direction inside the case and separately from the rod biasing member, and that biases the rotation cam toward the jutting out direction.