Under the influence of COVID-19, many companies in Europe and the United States are actively adopting telecommuting and teleworking, and they are becoming aware of the advantage of this work style, and it is believed that even after the pandemic is over, many companies will continue to let workers work from home. More generally, the experience of COVID-19 is going to bring about irreversible societal changes in working styles. On the other hand, the promotion of teleworking and telecommuting under COVID-19 has been relatively limited in Japan. This paper shows that there is also a significant gender gap in opportunities to work from home under the influence of COVID-19 in Japan, and women, who are considered to have a higher preference towards working from home than men due to the greater work-life balance it provides, actually have less opportunity to telecommute or telework than men. We will empirically clarify the determinants of this gender gap in opportunity. More specifically, the results of a decomposition analysis show that the gender gap in the opportunity to work from home is due to the gender differences in four factors: employment status (regular / non-regular employment), occupation, company's industry, and company's employee numbers. The results show that social structural factors that place men and women in different positions in the labor market are causing the gender inequality in opportunities for telecommuting and teleworking. This paper further clarifies the degree to which the different factors affect the gender gap, and also discusses their theoretical implications.