There is provided a film measuring device capable of accurately and easily measuring the thickness of a microporous film formed on a battery electrode plate over the entire area of the film. A color CCD sensor 8 shoots the microporous film. A video board 11 converts a color tone of a color image signal obtained by the image pickup into gradation data of respective color components of RGB. After the data conversion, an image processing board 12 extracts line images of the respective color components. A calculator 14 obtains the thickness of the microporous film by referring to pre-measured film thickness reference values corresponding to the gradation data of the green or blue color component, which are stored in a table storage 13 as reference thickness table data, using the gradation data of the line image of the green color component or the blue color component as lookup data.