In de Sitter space where the universe expands exponentially, any two of mutually separated regions eventually become causally disconnected. This is most conveniently described by spanning open universe coordinates on two open charts in de Sitter space. Recently, Maldacena and Pimentel showed that the entanglement entropy of a free massive scalar field between two open charts is non-vanishing. This result shows that two causally disconnected regions in de Sitter space are entangled. I extend the calculation of Maldacena and Pimentel to the case where a bubble wall is present between the two open charts. This can be thought of as a model of pair creation of bubble universes in de Sitter space. I will discuss the effect of the bubble wall on the entanglement entropy between the bubble universes.