A yarn winder comprising: a base; a bobbin holder which is cantilevered by the base and extends in a horizontal direction, bobbins on which yarns are wound, respectively, being attached to the bobbin holder along an axial direction of the bobbin holder; a contact roller which extends in the axial direction and applies a contact pressure to packages formed by winding the yarns onto the respective bobbins; a roller supporting member which supports the contact roller to be rotatable; a fluid pressure cylinder which is configured to posturally change one end portion in the axial direction of the roller supporting member at least in a vertical direction; and an intervention mechanism which intervenes between the one end portion of the roller supporting member and the fluid pressure cylinder, the intervention mechanism being configured to increase the thrust force (F1a, F1b, F1c) of the fluid pressure cylinder required to further move the one end portion of the roller supporting member as the fluid pressure cylinder increases a postural change amount of the one end portion of the roller supporting member in the vertical direction, characterized in that the fluid pressure cylinder includes a piston rod, the intervention mechanism includes a first intervention portion which includes a pressed member pressed by the piston rod and a supporting portion directly or indirectly supporting the one end portion of the roller supporting member, the first intervention portion being supported by the base via a first fulcrum shaft to be swingable in an up-down direction, and the horizontal distance between a part of the pressed member, at which part the pressed member is in contact with the piston rod, and the first fulcrum shaft decreases as the fluid pressure cylinder increases the postural change amount of the roller supporting member. a base; a bobbin holder which is cantilevered by the base and extends in a horizontal direction, bobbins on which yarns are wound, respectively, being attached to the bobbin holder along an axial direction of the bobbin holder; a contact roller which extends in the axial direction and applies a contact pressure to packages formed by winding the yarns onto the respective bobbins; a roller supporting member which supports the contact roller to be rotatable; a fluid pressure cylinder which is configured to posturally change one end portion in the axial direction of the roller supporting member at least in a vertical direction; and an intervention mechanism which intervenes between the one end portion of the roller supporting member and the fluid pressure cylinder, the intervention mechanism being configured to increase the thrust force (F1a, F1b, F1c) of the fluid pressure cylinder required to further move the one end portion of the roller supporting member as the fluid pressure cylinder increases a postural change amount of the one end portion of the roller supporting member in the vertical direction, characterized in that the fluid pressure cylinder includes a piston rod, the intervention mechanism includes a first intervention portion which includes a pressed member pressed by the piston rod and a supporting portion directly or indirectly supporting the one end portion of the roller supporting member, the first intervention portion being supported by the base via a first fulcrum shaft to be swingable in an up-down direction, and the horizontal distance between a part of the pressed member, at which part the pressed member is in contact with the piston rod, and the first fulcrum shaft decreases as the fluid pressure cylinder increases the postural change amount of the roller supporting member.