We can bulk approve the invoices by navigating through Transactions > Sales > Approve invoices.
To use this feature we have to create a workflow for the approval process of invoices. After creating the workflow, we can choose workflow actions in the Action field on the bulk approve page. After choosing workflow action, the invoices which satisfy workflow conditions will list on the bulk approve page. So user can select the invoice record and click submit button to approve all selected invoices.
