An internal structure of Pt field emitters fabricated by electron-beam-induced deposition (EBID) was investigated by in situ transmission electron microscopy during field emission and field evaporation. The internal structure of Pt field emitters was unchanged during field emission with an emission current of less than 480 nA. On the contrary, the top of Pt field emitters was sharpened after field evaporation. The Pt nanocrystals also moved to the Pt tip top after field evaporation. These results indicate the possibility of the sharpening of Pt field emitters by field evaporation, which would improve the field emission properties of Pt field emitters fabricated by EBID.