A curtain wave forming mechanism is constituted of curtain runners and a curtain hook attached to each curtain runner and hanging a curtain. The curtain hook is a separate body from a curtain tape and has a flat plate-like body section inserted into a hook insertion hole section of the curtain tape perpendicular to the length direction of a curtain rail, a foot section bent upward at the lower end central part of the body section and hooked to the hook insertion hole section, a shaft section extending from the upper central part of the body section, and a head section for insertion, formed on the head of the shaft section. A curtain runner has a body running in the curtain rail, a leg section hanging from the curtain rail, a hollow-cylindrical body supported at the leg section so as to be rotatable about the vertical axis of the leg section, and a bearing section for an insertion hook, supported at the hollow-cylindrical body.