The 24-year-old came into the World Championships in good form having secured a second-place finish in Germany last weekend but romped to victory in a four-man final.
Chapuis saw off competition from Finland's Jouni Pellinen and America's John Teller as well as his fellow Frenchman Midol as he came through in the final after winning both his quarter and semi-final races.
In the women's race Switzerland's Fanny Smith beat reigning World Cup champion Marielle Thompson of Canada to become world champion for the very first time.
The 20-year-old saw off the challenge of Thompson, France's Ophelie David and compatriot Jorinde Mueller to race to victory but she didn't have it all her own way en route.
In the semi-final Smith was in last place but managed to finish in second to qualify for the final where she made no such mistake.