A display device includes a first substrate which is light transmissive and has a display region and a periphery region surrounding the display region. A light shielding portion is formed in at least the periphery region of the first substrate and has a light passing portion in the periphery region. A first scale mark portion is formed on the first substrate so as to be arranged inside the light passing portion. A second substrate overlaps the first substrate and a second scale mark portion is formed on the second substrate and forms a pair with the first scale mark portion. A sealing member seals the first and second substrates in the periphery region between the display region and the light passing portion. A dam portion is formed on the first substrate between the display region and the light passing portion.