Provided is a voltage monitor, comprising an instrument box, wherein the instrument box is internally provided with a processor of ARM core integrated upon a circuit board, a voltage acquisition module, a GPRS wireless communication module, and an LCD module. The voltage monitor is special in that: the GPRS wireless communication module is arranged at the side edge of the circuit board; the side edge of the instrument box corresponding to the card-containing area of the GPRS wireless communication module is provided with a GPRS-use jack; and the voltage acquisition module is provided with a set of signal acquisition terminals. Compared with the conventional voltage monitor, the voltage monitor of the utility model reduces the land occupation area, reduces the installation and maintenance cost, and raises the economic benefits.