Two Higgs doublet model (2HDM), in which one more Higgs doublet is added to the Standard Model(SM), is one of the most simple extensions of the SM. 2HDM allows a solitonic object called as the Nambu monopole, which is a magnetic monopole attached with two vortex strings.
We show that the monopole is topologically stable when the Higgs potential has a global U(1) symmetry and a $¥mathbb{Z}_2$ symmetry. We also discuss phenomenological implications of the monopole. This talk is based on arXiv:1904.09269 and 2003.08772.