A tertiary olefin is produced by making a gaseous tertiary ether usually represented by the following general formula: ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are alkyl groups each having 1-4 carbon atoms which may be same or different each other and R.sup.4 is an alkyl group having 1-3 carbon atoms, contact a catalyst obtained by calcining a silica-alumina compound at 700.degree.-1100.degree. C. in order to carry out cracking of the tertiary ether.