The invention provides a measurement device and a measurement method for film thickness, and belongs to the field of photoelectric detection. A laser is used for transmitting laser to be functioned on the surface of a material through a focus lens, so as to generate a laser plasma flashing signal; the laser passes through the focus lens and a band elimination filter, enters a photoelectric detector, and then is converted into a voltage signal processed by a processor through an oscilloscope; when the laser energy is large enough, the laser punctures a film material, appears a pit in a flashing intensity curve of a laser-induced plasma, and a linear relation is formed between the time of appearing the pit and the thickness of the film material. According to the measurement device for the film thickness provided by the invention, expensive micro instruments, such as an AFM (Atomic Force Microscope), cannot be needed, the environmental requirement is lower, no tool contact is caused in an integral measurement process, and the cost of changing the measurement tool can be saved and changed; furthermore, the measurement device is easy to operate and is convenient for a worker to use, and can be integrated on an automatic production line, thereby being likely to be popularized and applied in an industrial field.