Despite numerous studies that have demonstrated widening gender inequalities during the COVID-19 pandemic, we do not yet see research on whether the surge in gender inequalities in socioeconomic lives would also have unequal consequences for women’s and men’s subjective experiences. In this talk I focus on the impact of gender inequality in childcare on the gender gap of mental well-being. By linking the countrywide Understanding Society COVID-19 longitudinal survey with the latest wave of the main-stage survey in the UK, I first confirm that the gender gap in time spent on parenting has widened during the lockdowns resulting from the COVID-19 pandemic, with mothers spent almost 10 hours more per week than fathers on home schooling and childcare for children under age 16. Regarding mental well-being measured by GHQ-12 (General Health Questionnaire), my findings are in line with the widely accepted arguments; namely, women are more distressed than men and parents with children under age 16 are more distressed than their counterparts who are not parents or whose children are older. What my study adds to the literature is about the widening gender gap in mental well-being due to the unequal share on childcare/ parenting. Although the presence of dependent children in the household has an equal, negative impact on mental well-being of mothers and fathers during the pandemic lockdowns, it does not increase time investment on parenting equally for mothers and fathers. Mothers spend significantly more time on parenting/ childcare during the lockdowns, which drives the worsening mental well-being for mothers compared to that of fathers.