A retaining device for a PCI card (30) includes a chassis (50), a retaining plate (20) configured for retaining the PCI card, and a mounting apparatus (10). The chassis has a rear wall (52). The rear wall has two clipping portions (526) and a perpendicular portion (52). The retaining plate includes an end (22) abutting on the perpendicular portion of the rear wall of the chassis. The mounting apparatus includes a mounting strip (11), and a mounting bracket (13) resisting on the end of the retaining plate. The mounting strip includes an elongated main body (12) with a handling portion (127) formed in the middle thereof and two arms (15) extending from two ends of the main body for engaging with the clipping portions respectively. The mounting strip abuts on the mounting bracket.