This study investigated the characteristics of natural groundwater colloids by a laser-induced breakdown detection (LIBD) and inductively-coupled plasma mass spectrometry (ICP-MS) in a combination with an asymmetrical flow field-flow fractionation (AsymFFFF). The groundwater was sampled from a borehole in the Yuseong area of Daejeon, Korea at different geological depths from 30 to 460 m and its geochemical parameters were measured. The combination of AsymFFFF and LIBD revealed a heterogeneous size fraction with a relatively broad size distribution of the groundwater colloids. One of the size fractions of the groundwater colloids was about 20 nm up to smaller than 100 nm, and the other fractions were larger than 100 nm. The elemental composition of the groundwater colloids was also analyzed by the AsymFFFF coupled with an ICP-MS. Results from the ICP-MS coupled with the AsymFFFF provided us with information about the size-specific elemental composition. The smaller sized fractions mainly consisted of calcite colloids with strontium, whereas the larger fractions were comprised of colloids such as aluminosilicates and iron oxides. The observations of all the groundwater samples indicate a similar pattern for the colloid fractions in size and in element composition except in the concentration.