An oil supply device for a linear motion guide device including a guide rail and a slider, the oil supply device comprising: a storing member which holds a lubricant; an applicator for applying the lubricant to the guide rail; and a container which accommodates the applicator and the storing member and can be installed on an end portion in a longitudinal direction of the slider, wherein in the container, a storing member accommodation portion which accommodates the storing member and an applicator accommodation portion which accommodates the applicator are provided, which are arranged in a direction in which the slider straddles on the guide rail, the direction being perpendicular to a longitudinal direction of the guide rail; wherein a communication hole for guiding the lubricant held in the storing member to the applicator is formed in a partition portion which partitions the applicator accommodation portion and the storing member accommodation portion, wherein the communication hole includes a small diameter portion which is positioned on the applicator accommodation portion side and a large diameter portion which is positioned on the storing member accommodation portion side and is larger than the small diameter portion, characterized in that the storing member is provided with a protrusion portion which is capable of fitting into the large diameter portion, and with a small protrusion which is capable of fitting into the small diameter portion of the communication hole wherein the protrusion portion and the small protrusion of the storing member are fitting and inserted into the communication hole such that the small protrusion is in contact with a surface of the applicator. a storing member which holds a lubricant; an applicator for applying the lubricant to the guide rail; and a container which accommodates the applicator and the storing member and can be installed on an end portion in a longitudinal direction of the slider, wherein in the container, a storing member accommodation portion which accommodates the storing member and an applicator accommodation portion which accommodates the applicator are provided, which are arranged in a direction in which the slider straddles on the guide rail, the direction being perpendicular to a longitudinal direction of the guide rail; wherein a communication hole for guiding the lubricant held in the storing member to the applicator is formed in a partition portion which partitions the applicator accommodation portion and the storing member accommodation portion, wherein the communication hole includes a small diameter portion which is positioned on the applicator accommodation portion side and a large diameter portion which is positioned on the storing member accommodation portion side and is larger than the small diameter portion, characterized in that the storing member is provided with a protrusion portion which is capable of fitting into the large diameter portion, and with a small protrusion which is capable of fitting into the small diameter portion of the communication hole wherein the protrusion portion and the small protrusion of the storing member are fitting and inserted into the communication hole such that the small protrusion is in contact with a surface of the applicator.