How to create custom fields of standard or custom object through apex code?

Hi Tanu,

You can refer to Metadata API document. Also please have a look on below code:

CustomObject co = new CustomObject();
co.setFullName(objectName+"__c");
co.setDeploymentStatus(DeploymentStatus.Deployed);
co.setDescription("Created by the WSC using the Metadata API");
co.setLabel(displayName);
co.setPluralLabel(displayName+"s");
co.setSharingModel(SharingModel.ReadWrite);
co.setEnableActivities(true);

// create the text id field
CustomField field = new CustomField();
field.setType(FieldType.Text);
field.setDescription("The custom object identifier field");
field.setLabel(displayName);
field.setFullName(objectName+"__c");
// add the field to the custom object
co.setNameField(field);

AsyncResult[] ars = metadataConnection.create(new CustomObject[] { co });

Thanks