To understand the consumers’ purchasing behaviour of green products, this study aims to know the different effects of socio-economic factors (gender, age, level of education, and level of income) on the environmental concern and knowledge owned by the customer through Analysis of Variance (ANOVA) statistic-test.  This study used primary data that were collected through an online and offline questionnaire. In this study, 510 respondents located in the city of Semarang in Indonesia participated in the online and offline questionnaire, however, only 325 answers were valid. As a result of the ANOVA statistic-test, this study found that a significant difference among consumers of different ages, gender, and level of education in terms of environmental concern and knowledge. The customer with age group less than 30 have, female, and level of education senior high school and university have a mean value of environmental concern and knowledge higher than the other groups. On the other hand, this study fails to prove a significant difference among consumers at a different level of income in terms of environmental concern and knowledge. The analysis used in the study gives important insights into the different effects of a socio-economic factor on environmental concern and knowledge to encourage the customer to purchase the green product. The study extends the existing literature related to the purchasing behaviour of the green product and also offers managerial implications for the manufactures to strengthen green marketing activities based on socio-economic factors.