An imaging apparatus to which any one of lens apparatuses including a first lens apparatus and a second lens apparatus is detachably mountable, the imaging apparatus comprising: a mount unit, and a contact holding member provided to the mount unit where a plurality of electric contacts (1001 - 1012) are arrayed, wherein the plurality of electric contacts (1001 - 1012) includes: a first electric contact group (1006, 1007, 1008) used to perform first communication with a lens apparatus mounted to the imaging apparatus, a second electric contact group (1009, 1010, 1011) used to perform communication that is different from the first communication with a lens apparatus mounted to the imaging apparatus, a first power contact used to supply first power and configured to become a high potential side when the first power is supplied, and a second power contact used to supply second power and configured to become a high potential side when the second power is supplied, wherein the imaging apparatus is configured to perform communication using the first electric contact group (1006, 1007, 1008) with both of the first lens apparatus and the second lens apparatus, wherein the imaging apparatus is configured to perform communication using the second electric contact group (1009, 1010, 1011) with the second lens apparatus but is configured not to perform communication using the second electric contact group (1009, 1010, 1011) with the first lens apparatus, wherein the contact holding member has two tiers each of which holds electric contacts included in the plurality of electric contacts, wherein the first electric contact group (1006, 1007, 1008) and the second electric contact group (1009, 1010, 1011) are held on one of the two tiers and the first power contact and the second power contact are held on the other of the two tiers, and wherein, where a direction of rotation of the second lens apparatus with respect to the imaging apparatus when mounting the second lens apparatus to the imaging apparatus directly is a first direction, the second electric contact group (1009, 1010, 1011), the first electric contact group (1006, 1007, 1008), the first power contact and the second power contact are arrayed in the order of the second electric contact group (1009, 1010, 1011), the first electric contact group (1006, 1007, 1008), the second power contact and the first power contact in the first direction. a mount unit, and a contact holding member provided to the mount unit where a plurality of electric contacts (1001 - 1012) are arrayed, wherein the plurality of electric contacts (1001 - 1012) includes: a first electric contact group (1006, 1007, 1008) used to perform first communication with a lens apparatus mounted to the imaging apparatus, a second electric contact group (1009, 1010, 1011) used to perform communication that is different from the first communication with a lens apparatus mounted to the imaging apparatus, a first power contact used to supply first power and configured to become a high potential side when the first power is supplied, and a second power contact used to supply second power and configured to become a high potential side when the second power is supplied, a first electric contact group (1006, 1007, 1008) used to perform first communication with a lens apparatus mounted to the imaging apparatus, a second electric contact group (1009, 1010, 1011) used to perform communication that is different from the first communication with a lens apparatus mounted to the imaging apparatus, a first power contact used to supply first power and configured to become a high potential side when the first power is supplied, and a second power contact used to supply second power and configured to become a high potential side when the second power is supplied, wherein the imaging apparatus is configured to perform communication using the first electric contact group (1006, 1007, 1008) with both of the first lens apparatus and the second lens apparatus, wherein the imaging apparatus is configured to perform communication using the second electric contact group (1009, 1010, 1011) with the second lens apparatus but is configured not to perform communication using the second electric contact group (1009, 1010, 1011) with the first lens apparatus, wherein the contact holding member has two tiers each of which holds electric contacts included in the plurality of electric contacts, wherein the first electric contact group (1006, 1007, 1008) and the second electric contact group (1009, 1010, 1011) are held on one of the two tiers and the first power contact and the second power contact are held on the other of the two tiers, and wherein, where a direction of rotation of the second lens apparatus with respect to the imaging apparatus when mounting the second lens apparatus to the imaging apparatus directly is a first direction, the second electric contact group (1009, 1010, 1011), the first electric contact group (1006, 1007, 1008), the first power contact and the second power contact are arrayed in the order of the second electric contact group (1009, 1010, 1011), the first electric contact group (1006, 1007, 1008), the second power contact and the first power contact in the first direction.