The gas electron multiplier (GEM) detector is a promising particle and radiation detector which has been greatly improved from previous gas detectors. In particular, the 10 cm × 10 cm GEM detector is utilised in applications including highresolution tracking devices in nuclear and particle physics. With its operational and design simplicity, while still maintaining high quality, the GEM detector is suitable for both start-up and advanced research. This article reports simple procedures and results of an investigation of important properties of this detector, using current measurement and signal counting. Results show that gains of the GEM detector increase exponentially as voltages supplied to the detector increase and that the detector reaches full efficiency when the voltages are greater than −4100 V. In terms of signal sharing between X and Y strips of the read-out, the X strips, on the top layer of the read-out, collect larger signals. For the uniformity test, the GEM detector has slightly higher efficiencies at the centre of the detector. These results can be used for future reference and for better understanding of the GEM detector’s characteristics.