Provided is a device for capturing an image of a pantograph by a line sensor camera (1) attached to a vehicle and measuring the vertical acceleration of the pantograph on the basis of the image captured by an image processing unit (2), wherein the image processing unit (2) is provided with an image input section (21) for inputting the image at a measurement point of the pantograph captured by the line sensor camera (1), a pantograph position detection section (23) for performing image processing on a line sensor image produced from the input image to thereby find the position of the pantograph on the line sensor image, and a pantograph vertical acceleration calculation section (24) for calculating the vertical acceleration at the contact point of the pantograph with a trolley line on the basis of the position of the pantograph on the line sensor image, previously found one or more transfer functions, and the deviated position of the pantograph. Thus, the vertical acceleration of the pantograph can be measured with high precision by the compact device.