A microneedle device system, comprising: a microneedle device (600a, 600b, 600c, 600d, 600e, 600f, 600g, 600h, 600i, 600a', 600b', 600c', 600d', 600e', 600f, 600h', 600i') having a sheet-like microneedle having a sheet in which one surface is a skin contact surface and the other surface is a rear surface and whose one portion is a skin piercing region, in which a plurality of microneedles are formed substantially along a surface of the sheet, and in which the microneedles in the skin piercing region are designed to be raised from the skin contact surface so as to be capable of piercing skin if the sheet is bent in a thickness direction, an adhesive layer (610, 620, 630, 640) that is disposed on the sheet-like microneedle, and a liner that is attached to the adhesive layer (610, 620, 630, 640) so as to be releasable therefrom; and an auxiliary tool (700, 1500) which has a bending portion (1550, 100A) for bending the microneedle device (600a, 600b, 600c, 600d, 600e, 600f, 600g, 600h, 600i, 600a', 600b', 600c', 600d', 600e', 600f, 600h', 600i') in the thickness direction, and on which the microneedle device (600a, 600b, 600c, 600d, 600e, 600f, 600g, 600h, 600i, 600a', 600b', 600c', 600d', 600e', 600f, 600h', 600i') is mounted so as to be movable along the bending portion (1550, 100A), wherein the liner has a function to raise the microneedles. a microneedle device (600a, 600b, 600c, 600d, 600e, 600f, 600g, 600h, 600i, 600a', 600b', 600c', 600d', 600e', 600f, 600h', 600i') having a sheet-like microneedle having a sheet in which one surface is a skin contact surface and the other surface is a rear surface and whose one portion is a skin piercing region, in which a plurality of microneedles are formed substantially along a surface of the sheet, and in which the microneedles in the skin piercing region are designed to be raised from the skin contact surface so as to be capable of piercing skin if the sheet is bent in a thickness direction, an adhesive layer (610, 620, 630, 640) that is disposed on the sheet-like microneedle, and a liner that is attached to the adhesive layer (610, 620, 630, 640) so as to be releasable therefrom; and a sheet-like microneedle having a sheet in which one surface is a skin contact surface and the other surface is a rear surface and whose one portion is a skin piercing region, in which a plurality of microneedles are formed substantially along a surface of the sheet, and in which the microneedles in the skin piercing region are designed to be raised from the skin contact surface so as to be capable of piercing skin if the sheet is bent in a thickness direction, an adhesive layer (610, 620, 630, 640) that is disposed on the sheet-like microneedle, and a liner that is attached to the adhesive layer (610, 620, 630, 640) so as to be releasable therefrom; and an auxiliary tool (700, 1500) which has a bending portion (1550, 100A) for bending the microneedle device (600a, 600b, 600c, 600d, 600e, 600f, 600g, 600h, 600i, 600a', 600b', 600c', 600d', 600e', 600f, 600h', 600i') in the thickness direction, and on which the microneedle device (600a, 600b, 600c, 600d, 600e, 600f, 600g, 600h, 600i, 600a', 600b', 600c', 600d', 600e', 600f, 600h', 600i') is mounted so as to be movable along the bending portion (1550, 100A), wherein the liner has a function to raise the microneedles.